Either S6 will be about undoing S5 or you can wave those story threads bye-bye
If S5 ends like the leaks claim, it ends by creating a new reality where only a handful of people will be aware that the world was re-set:
Marinette, who witnesses The Wish being made and somehow remembers the past that was destroyed to create the new reality
Presumably Lila who is also present and knows enough to steal the butterfly miraculous afterwards
Su-Han and Alya, who will be told by Marinette
Possibly Emilie, Nathalie, Tomoe, Felix, Kagami and the rest of the kwamis who canonically know who it was that had Hawkmoth's miraculous
As far as everyone else is concerned, Emilie Agreste never died and Nathalie Sancoeur never walked around with an exoskeleton.
There are some problems with this.
IT'S CONTRADICTING THE ESTABLISHED LORE ABOUT HOW THE WISH WORKS
Per Sass' explanation to Luka in "Ephemeral", The Wish "erases" reality and creates a different one. This means that the only way Emilie can be alive is if she never died, and the only way for Emilie to not have died is if she never used a broken miraculous in the first place, meaning that
a) Someone else used the broken peacock miraculous and croaked a few months before "Origins"
b) The peacock miraculous wasn't broken when she used it (this means Colt also didn't die from it, giving Felix a significantly different backstory)
So we're gonna need the explanation for which one of those it was, but more importantly: We're gonna need an explanation for how the hell the entirity of canon even happened at all.
Because Ladybug and Cat Noir exist because Hawkmoth attacked Paris, and Hawkmoth attacked Paris for the sole purpose of undoing Emilie's death.
But in the reality where Emilie is alive, what reason did Gabriel have for this asshattery? What drove him to become a cackling villain in a world where he doesn't have the excuse of lacking grief counceling?
One obvious answer would of course be that Hawkmoth in this reality wasn't Gabriel at all, but that would mean that Hawkmoth's war on Paris would be significantly different from the one depicted in-story, and that Ladybug and Cat Noir's relationship would be shaped by different experiences than the ones they shared in the old reality. And there were a number of akumas caused directly by Gabriel's caustic personality and just... wouldn't, here. Moreover, Lila still got the butterfly miraculous from the villain lair that was in Gabriel's home, and most of the plot development in seasons 3-5 are the result of Felix' vendetta against him.
Canon can only happen if Gabriel Agreste is Hawkmoth, but Gabriel Agreste has no reason to be Hawkmoth when his wish is fulfilled.
By all accounts, it doesn't make sense.
IT UNDOES THE PREVIOUS CHARACTER ARCS
We might never know what the Agreste family life was like in this reality where Gabriel never turned into a bitter widower resorting to supervillainy. Adrien, in this reality, never lost his mother and has never lived with an abusive father and a couple of employees enabling him.
Adrien's active rebellion against his father in S5 might be the most tangible character development anyone on this show has gone through, but that relies on his having something to rebel against. In a reality where Gabriel never was the asshole he is in the previous universe, Adrien would have no reason to go through this process. He never had to grieve his mother, he never had to lose his father to the same grief, he never had to suffer his father's emotional neglect and supervillainy abuse and presumably not his direct slavery to the amok rings being used against him. (we don't talk about wishmaker no no no)
The Adrien in the re-written universe never went through the journey because he never needed to; by all logic, the lack of these experiences should mean that he is a fundamentally different person. To him, Cat Noir's antics can't have been about letting out a joie de vivre that is forbidden in his civillian life, can't have been an escape from a home that is a prison, can't have been the only self that had true agency. Ladybug can't have been his first true friend, can't have been the only person who gave him the belonging and unconditional acceptance that his father refused him and the classmates who never saw all of Adrien ever could. If Adrien wasn't desperately lonely and repressed, then Cat Noir is just a clown for the hell of it.
The same would logically apply to any character growth that involves Gabriel Agreste rather than Hawkmoth. Felix' game of miraculous chess against his uncle, Kagami's escape from the adrigami arranged marriage BS, Marinette telling Gabriel to suck his own dick, Nathalie making the choice between Adrien and Gabriel and choosing the one we didn't expect - none of that can happen in a reality where Gabriel was always a good man and a good father. But given that all these characters presumably remember the old reality, only Adrien - ironically the person who by far was the deepest hurt by Gabriel's cruelty - is affected by the past being undone.
What remains would be Chloé's rise and fall in S2-3, if Thomas Astruc hadn't helpfully tweeted that that was all in our heads.
IT WRAPS UP NICELY SO WHY EVER TALK ABOUT IT AGAIN
Marinette's (and Plagg's, Felix', Kagami's, Emilie's, Nathalie's, Alya's) choice to let Adrien live in happy ignorance about his father's sins means that we can have the completely happy ending: Adrien grieving Gabriel's heroic death is the only negative here, with everything else having sorted itself nicely: Hawkmoth is gone, Ladybug's team is restored, no children live with abusive parents except Chloé and anyway she deserves it, right, being a sentimonster is no longer a problem with everyone having their own amok and Felix having Duusuu, the new villain rising is someone who everyone hates and no-one will be hurt to see her eventual defeat.
By all accounts, they've wrapped the story up with a bow on top. No-one wins anything by bringing any of this up again, no-one needs to be plagued by an ill conscience, and any audience demand that Adrien get to face the truth would be sadism. Bring out Ibsen if anyone quarrels.
As anyone with half a brain and this fandom's penchance for analysing the show beyond everything the writers intended, This Is Problematic.
S4 had a running storyline about Marinette choosing to rely on Alya, Su-Han and on one memorable occasion, bloody Luka over the partner who was at her side before any of them, and though it ended with her announcing her regret abut this, S5 has yet to see her make up for it. She still hasn't told him about Alya/Rena Rouge being promoted to her first mate above him; about that time she tried to trick him into revealing his identity to two different third parties, or as the fandom loves to bring up (though the show has firmly ignored it) that timeline where he knew her identity and got akumatised and destroyed the world.
The S5 ending doubles this transgression; not only will she not tell Cat Noir about what really happened with the enemy he alone has been fighting at her side since the very beginning while she will tell at least two other parties about it - she will be denying Adrien the same truth, and deny him the ability to take a stance about his father. Can Gabriel's sins be forgiven? The writers might leave that one technically unanswered, but Marinette is making that choice on Adrien's behalf. Not only is she continuing the S4 sins she claimed to regret to his face; she's betraying him as his girlfriend as well, choosing instead to stay loyal to his abusive father.
A number of third parties are keeping similar secrets - Rena Rouge and Su-Han from Cat Noir; Alya, Felix, Kagami, Nathalie and Emilie from Adrien, and Plagg (and Tikki) from both sides of him. As S5 ends, Adrien's happiness and peace of mind is built on a gigantic lie of which enough people know that it would take very little to pull the rug out from under him.
Particularly since the only thing keeping Lila from revealing any of this is would be either the ability to extort either Ladybug, or Felix/Nathalie/Emilie with the threat of revealing the truth to Adrien. If that ever becomes a storyline, Lila would ironincally become a force of justice because "the truth would just upset you" is not an excuse that holds up under any kind of scrutiny.
Adrien, by the nature of his creation, can be enslaved by any rando who happens to get a hold of his parents' wedding rings. The same wedding rings, if damaged or destroyed, will instanty end Adrien's life. Because Adrien will be denied the truth about his parents' business with the peacock miraculous, he'll also be living ignorance about the fragility of both is self-determination and his very existence.
This in a show where the very plot is built on jewelry being lost and found.
This in a story that has repeatedly made it a Point that Adrien's father has deprived him of agency, has kept him imprisoned in his home, has made him a servant to his own whims and has outright used his amok against him. The show has repeatedly highlighted that Adrien needs to break free, but not only is Adrien's escape un-done by the re-created timeline - Adrien is handed the keys to his cage without explanation, and a number of people who could inform him of how vital the safekeeping of the rings are will refrain from doing so in order to let him live in blissful ignorance, seemingly hoping he's sentimental enough to not have the rings melted down into a pair of cufflinks or give one of them to any present or future girlfriends.
That number of people is his mother, his surrogate mother who might be the only person fully comprehending the extent of his father's abuse, his cousin who shares the same grim fate, his still friendly ex who should by now realise what it was that made her break up with him because she also shares that curse, his girlfriend, and his kwami. And possibly Alya, depending on how much of the story Marinette will tell her.
In short: forget about Adrien being upset about learning the truth about his father now. If Adrien ever learns about how every important person in his life (except Nino) has been keeping vital information from him Out Of His Own Good, we've got a shitstorm coming that will make Cat Blanc look like Hello Kitty.
THE MILLION DOLLAR QUESTION: IS THE SHOW EVER GOING TO ADDRESS THIS?
I obviously don't know, but I noted the following:
Cat Blanc had 20 seconds of screentime in S4 and has yet to be brought up in S5
"Kuro Neko" ended the supposed ~ladynoir conflict~ with telling us all that Ladybug Was Right, and even though she might've claimed otherwise at the end of "Strikeback", the show hasn't in fact proven her wrong or done anything to make up for her alleged sins
Keeping Your Identity Secret is the rule every superhero must obey because Hawkmoth might attack you and your family. Except if you're Carapace, Pegasus, King Monkey, Viperion or Ryuko, then it's fine if he knows. And if you're Bunnix or Argos, arguably the two most potentially ruinois powers if abused, then it's okay that the whole fucking world knows your identity.
By which I mean: Miraculous Ladybug is exceptionally good at ignoring, disregarding or downplaying its own story points if they make things too uncomfortable for our heroes. Despite the fact that I've spent three nights typing up this whole sorry story, I don't take a huge issue with this. I prefer the show as a stupid superhero rom-rom and I don't much care for the larger story or its internal consistencies as long as I get to watch Ladybug and Cat Noir be cute and funny while fighting villains.
But I wouldn't bet real money on seeing any of these storylines resolved on-screen.
