for me, THE main reason I think the show is gonna go with the romantic route, is the hamachi dish.
in s1, we get to know that Sydney's best meal was what Carmy made in New York
in s3, we get to know how much abuse he took in new york, how with the fennel it wasn't his dish anymore, but was forced to make that way, and that one day, after Mikey died, he said fuck it, this plate, this one plate is gonna be mine, he rebelled against the abuse, and that one plate was the one Sydney got. The one that was life-changing, and probably was a big part of why she took the job at the Beef. (And also, it looked like a bleeding heart.) She had a taste of the best of him, that spark that was there despite all the abuse, the anxiety, the sudden grief and guilt, that spark that in s4, we know he can't draw from anymore. and that best part was the best she ever had.
in s4, Sydney tells Donna that she flew to new york, becuse she wanted to taste his food so badly, and hands down that was the best meal of her life, and that "i don't even know if he knows this"
They keep bringing this up, telling us that he doesn't even know this. Why is it important? It could be professional reasons. That they are really platonic soulmates in the kitchen, that she's gonna be his legacy - he made her best meal, now she's gonna do the same to someone else.
And it would make sense, because season 4 was all about that:
in s3, they have a talk about legacy, and if he's gonna leave something behind, he wants it to be panicless, anxiety-free, he has to filter out the bad to make it good
and in s4, we see the absolute calmest, almost sensual sequence with Sydney making the scallop dish, then he sees her plate the cavatelli under 3 minutes, without even really trying, when that's something even he couldn't do, and realizes, that this is it. Syd is the panicless, anxiety-free version of the restaurant, that he can leave behind. And to make it good, he has to filter out the bad, aka himself, and he has to leave to change, it's the best for the restaurant and him (and he believes for everyone, including Sydney).
him realizing that she's just plain better than him, and more, she's better without all that extra trauma he had to endure to get to that level
and that, well, is painful for him, and is jealous a bit (as Sydney tells TJ, he acts weird and funky with her when she's better), but the season shows us that he ends up accepting it, embracing it, welcoming it (he fully expects her to get that best chef title, with a gentle smile on his lips, absolutely no jealousy or hurt there anymore) (also, there's a big visual emphasis on when he gives her his signature spoon, like it's her turn, she's his legacy)
And the revelation of the hamachi dish would fit in this so well. It could have been like: all the best that he still had in himself, he gave it to her, only her, and she ate it, she internalized it, and now it's hers, and he doesn't have it anymore. It would fit the legacy theme so well.
But they didn't do that. Instead, the crescendo of the theme is their arguing in the finale: "Syd, you're everything I'm never gonna be. I believe in you more than I believed in myself. You're The Bear."
And it feels final. Syd accepts it. She has self-doubt, of course, but she doesn't say "You're wrong." She says "And what if you're wrong." Because she knows it's true. "I know I don't need you." Their argument isn't about the restaurant. That's done. He knows it, she knows it.
So what else is there? What else could they use that reveal of the hamachi dish?
back to the legacy conversation, he says in order to leave something anxiety-free behind, he's gonna have to be square with everyone, and that's what we're seeing he's doing
he apologizes to Claire, calls her and tells her what he should've told her many-many times before, he finds her sweatshirt to give it back to her, to open up a way to see her again
he visits Donna, he lets her apologize, cooks for her, maybe it's a start to be in each other's life
I didn't put a picture, but he calls Cicero to thank him and telling him how much he appreciates him
at the news of him leaving, Nat is just plain happy for him, she hugs him, that's all she wanted for him, to get better, to find peace and joy
even with Richie, their argument came to an end, it was the revelation that he did in fact came to the funeral, he did resent Richie because he was more a part of his family than he was, and that he was blind to the fact the Richie lost someone, too. Then Richie confessed he feels the guilt, too, because he couldn't help Mikey, and he though that's why Carmy didn't go to there funeral. Richie tells him he resented him, too, and missed him. Carmy tells him they're more than cousins. They cleared the air.
However, Sydney and Carmy's argument wasn't over, it was interrupted by Richie. By then, it was already established that she's The Bear, she's everything he's never gonna be, and that she doesn't need him.
"but that's not the point" - Syd tells him, and it tells that it's not about the restaurant and whether or not she could do this without him
"you're my partner" "i'm your friend" "you're not acting like it" "i'm your fucking friend" - they are literally arguing about what they are to each other when Richie stops them
when Richie and Carmy fights, at the end of the scene, she already accepted that Carmy leaves - the reality of it at least, and now they have a new plan. So the emotional side of the restaurant's future - it's resolved.
more than that, when Nat asks Carmy "Bear?", like "tell me, is this true?", it's cut to Sydney and Carmy having a silent conversation, nodding to each other, as if Sydney is giving him some kind of "permission" to tell Nat, making it final, making it reality, and just after that he turns to Nat.
but the thing they last argued about, what they are to each other - it's not resolved in the slightest, not like with the other characters.
Carmy said in order to leave, he's gonna have to be square with everyone - and that leaves Syd in S5. It has to be some kind of change in their dynamic, some kind of turnover, and I think that the reveal of the hamachi dish will be the catalyst, like, the realization of love. (He literally gave her his one and only bleeding heart.)
Because they shouted "partner" and "friend" at each other - it would be really disappointing if the resolution of their conflict would be - yeah, we ARE partners and friends. I think it should be a third thing, one that they are both blind to at this point. Like, from a storytelling perspective.
So how I think will turn out? Well, we were given:
we were shown Sydney taking a picture of the hamachi dish
in s4, we were shown Sydney taking a picture of the lamb dish, inspired by her dress she wore at the wedding, where
Sydney's and Donna's conversation took place - Donna now knows how inspired Sydney is by her son, and that he cooked the best meal of her life, she says "wow", because yeah, that's a wild little coincident, and a good story
Carmy mentions the photos at his place, then Donna eventually got him to bring them to her, which leads to this:
"when I saw you at the wedding, and you're all grown, and you're this guy and so handsome, and I'm happy for you" and "people say such nice things about you and tell me how wonderful you are, and I hear about what you do" (that was all Sydney btw) "I hear about your life from other people, I don't know you and you don't know me and i did that, and I know that me saying this doesn't mean anything except that i'm trying, i'm trying to be responsible and accountable and apologize and trying to make things better" "and i'm here asking if i can be part of your life again"
she wants to know her son, because he lived a whole life she wasn't part of
So I can see her trying gather as much knowledge as she can about her kids, Carmy, looking and collecting articles, photos, then maybe reaching out to Sydney (maybe through Nat), asking if she has a photo of his dish, because it was so good to hear how her son did that, inspired someone so much. So maybe Sydney gives her a photo, and maybe Donna one day shows him an album she made about her kids, to show him that she's trying to get to know him. And he's turning the pages, smiling, then bam. He's facing a photo of the blood orange hamachi, and it's like he's hit by a train. It shouldn't be possible. How the fuck is this possible? So he asks Donna, and she tells him this cute story that his coworker told her at the wedding, and that she just had to ask for a photo... and the world is upside down, things clicking into place.
I think it would be such a satisfying revelation, and such a strong resolution to Carmy's and Sydney's interpersonal conflict of "what are we?", and I think with this route, it has to be romantic, bc what other resolution is there? "omg, she's INDEED my friend?" come on.
(btw, I'm literally writing a novel-length fic with this theory right now, bc i'm feeling feral about this idea)