While we're waiting for the Thunderbolt Fantasy final (sob) movie to come out, here are some of my predictions/wishes/hopes for what's going to happen:
-the demon gods are banished/sent back to their original realm. Once they are gone, there's no more need for the Shen Hui Mo Xie, so those will also go (probably also back to their original world, where they'll just be ordinary swords). I would love it if the Index became sentient and chose this fate, though!!
-Shang might use the scrying mirror he picked up from Xing Hai for one or both of these things OR he might save it for some secret timey-wimey thing bringing his own life full circle (although I really hope that isn't what actually happens). One way or another, he's gonna use it, though.
-with no more swords to guard, the Hu Yin Shi dedicate their lives to healing the world/Wasteland of Spirits, where their new fortress happens to conveniently be located. Unless the Lotus MacGuffin sword heals everything first???
-Bo Yang Hou dies. Sorry, old man, you represent the old ways, and also someone has to die in this movie for pathos, and I'd rather it be you than Juan Can Yun.
-Juan Can Yun and Dan Fei survive and have a million babies and rebuild the Dan clan; Urobuchi had BETTER not kill either of them off or I'll be so pissed.
-I would love it if the new Dan clan fighting style ends up as some combination of sword and spear techniques!!! Let Juan Can Yun use a spear again 2K25!!
-I think Lin's plan to target the Demon King will not provide him with the catharsis he seeks because it's not clear to me that the Demon King has the emotional capacity for the kind of reaction Lin craves. (He's like Locust in this way.) So regardless of how much disruption Lin causes, I think he'll be ultimately unsatisfied with the results.
-because of a dearth of "villains" in peacetime, Lin will give it (mostly) up and travel the world with Shang instead. One or both of them might ostensibly have a task to do, but I would love it if these two just wandered the jianghu and lived their best lives. Bonus if there is some dialogue that is suspiciously similar to wedding vows (technically, Lin already proposed with the whole "wrecking havoc on the world" line back at the beginning of S4, so all that's left is for Shang to take him up on it).
if this movie doesn't end with the two of them walking off into the sunset while "Darkest" plays, I'll be shocked. and the immediately go back to writing fanfics where this totally happened.
-Yan Xi becomes the ruler of a reunited Wan Yu because he's the only one left. Shu Liang Bi's headache gets deeper. Hopefully he gets a raise.
-Partway through S4, I thought Yan Xi and Chao Feng might get married for state reasons, but having embraced her obsession to become a Dark Magical Girl, Chao Feng is probably doomed. Lang is probably going to kill her, which is only going to make him spiral more. She might also have a Gollum-like role, where she accidentally does something good or useful while attempting to fulfill her own self-interest.
-hopefully Lie Mo Xian is human for good, but he might turn back into a pipa again when not in the demon realm, who knows
-character poems for Azi, Locust, Chao Feng, and Shang (redux), I think, although given that it's only 90 minutes, who even knows
-Azi vs. Lang fight. Hopefully Lang won't use the seals, but let's face it, he hasn't been making very good decisions lately, so he probably will. Killing Azi will bring him no joy, only more angst. and once he becomes a demon god, he'll start attacking the human realm.
(Bonus points if Azi's last words are "subarashii")
-Lang's demon god form will also be incredibly hot and different from his Azi-like "Awakened" form we saw briefly in S4.
-there's a picture on the official website of a giant 4-eyed demon god with an entire city/castle on its head peering out of a hole in the ground, so yeah, that's happening at some point
-please please please let Tian Ming's song be what brings Lang back from his Demon God rampage of revenge please please please. Also Shang and Lie Mo Xian, but LET TIAN MING DO SOMETHING
-also Lang and Tian Ming are probably an endgame ship
-I still don't know exactly what Locust has planned (probably becoming fate itself or something equally grandiose) or what his and the Demon King's fates will ultimately be (probably both dead) not to mention what Lin has planned for both of them and whether or not it will work…. but hopefully it'll be awesome.
-I would love a Lin vs. Demon King fight, or to see the Demon King fight at all.
-WHAT about those secret weapons Bo Yang Hou shipped across the Wasteland of Spirits???? PLEASE BE ANOTHER CANNON OR SOMETHING (but let's face it, it's probably more swords).
-anyway, the major conflicts as I see it are each of the heroes fighting their narrative foils/shadow selves (literally and figuratively): Lang vs. Azi; Lin vs. Demon King; and Shang vs. Locust.
-there's also a snippet in one of the S4 BTS videos with a clip of the Xi You army and a palanquin with the chancellor beside it, so presumably Chao Feng is going to try and get the Dong Li humans to surrender and/or double-cross them. Hopefully the Xi You forces will ultimately side with humanity instead of accepting the demons as allies.
Anyway, I'm really only scratching the surface here, and am probably missing a lot, but this is at least a good start.