Guardians of Light:
Sora
Riku
Kairi
Ventus
Aqua
Lea
Mickey
Though since Nomura has said that the Guardians and Darknesses won't be revealed until the end of the game, I'm expecting some massive plot twists. Like, maybe the freed Terra will end up replacing Lea?
I know a lot of people have theorized that Sora isn't actually a Light, and I could see Nomura doing something like that, but it seems too obvious. But then again, this site has predicted a lot of Nomura's twists before so maybe this could be a thing?
As for Roxas... I get why people think he could be a Light, I really do, but I think I'd prefer it if he wasn't. I still want him to fight Xemnas, don't get me wrong, but I think it would fit his character to moreso be a bystander for everything else. He never really wanted a life of fighting, anyway, and was clearly tired of it in II and longed for a life similar to that of the Twilight Town trio's. Same goes for Xion, and even Lea (though Lea will probably still be a Light).
Seekers of Darkness:
Master Xehanort
Xehanort's Heartless
Terranort
Xemnas
Vanitas
Isa
Braig
Young Xehanort
Master of Masters
Dilan
Even
Luxord's Somebody
Aeleus Rikunort or KH1!Riku
...I'm less sure about Aeleus, because it seemed that he was maybe content to just live a normal life in Radiant Garden during the events of Dream Drop Distance, but we'll see
Ansem the Wise could be one, but I doubt it. Repliku's a real possibility but I'm really hoping they just let him stay dead... There's Robed Xehanort and Apprentice Xehanort to consider, but I doubt those ones. Rikunort's a real possibility, though. Actually scratch Aeleus off my list.
Coded has all but convinced me that Rikunort, or past Riku, is one. Eraqus could also be a contender.
Now for outlandish Lights:
I would love love love love love it if Naminé was a Guardian of Light. Her design looks pretty light-like already, and it'd be a realistic twist, I think. It'd be great to see her having some agency and getting the chance to fight for once, too (though not with a Keyblade, please). Maybe this could confirm that Naminé was created from Kairi's light, or something, like some people have thought?
Make Donald and Goofy Lights. Just make them Lights, please. Let them be important again and BA like Mickey is, and keep the Guardians of Light from being all Keyblade wielders this way.
Ephemera, Skuld, and/or maybe Ava as Lights could be really cool. And likewise Eraqus in a surprising, last minute addition where he breaks free from Xehanort's--Terranort's--control and joins our heroes when things seem at their worst.
In this vein, also maybe Terranort or even Xemnas.
Yen Sid finally getting out of his chair and being a Light if he's called to be, perhaps.
Yen Sid's Master (whomever it may be)
Chirithy, because I could honestly see it of our sweet little companion, and no one would ever see it coming.
Player, though I doubt this one.
Ansem the Wise?
Young Xehanort
Braig (if this were to happen, I think we'd have Braig as a Light and Xigbar as a Darkness so there'd be two of him in the fight).
A freed Isa (though I really don't think so).
Demyx, Marluxia, and/or Larxene's Somebodies. Weird, I know, but if they wanted to get revenge on Xehanort and the Organization this would be the way to do it.
Master of Masters or Sixth Apprentice, if they're not evil (in which case they could be Darknesses); same thing goes for Xehanort and Eraqus' Master.
The Keyblade wielders we've helped out in Chi and Unchained Key in certain quests.
Some entirely new characters.
Outlandish Darknesses:
Sora, I could see it. Maybe he was infect with Xehanort's heart and we just didn't realize it. In fact, I swear that that was the original ending to DDD.
Kairi. I know it'll never happen, but I just love the idea that Xehanort put part of his heart into Kairi when she was missing hers, and that we'll have to fight time traveling, fourteen-year-old Xehanort-ified Kairi who finally talks of her own suffering.
Roxas and/or Xion. This one's not as outlandish for me, because I think either of these are a real possibility, tbh.
Lea. I've somewhat bought into HMK's theory about him and I'm not sorry.
Ven? The Ven that he was before his heart was ripped in two, though, so maybe someone more like Gula (if the Rebirth theory is true)?
Aqua... if the Realm of Darkness has screwed her up. I feel like 0.2 will somewhat being playing with our fear of that, but since we know she's A-Okay by Blank Points this probably won't happen.
Dark Chirithy?
Corrupted Foretellers?
Ephemera?
Player?
For some reason I can't see Skuld getting possessed, or whatever, and becoming a Darkness but who knows?
Ienzo? Really don't think so, tbh, but it's more likely than Demyx, Marluxia, and Larxene, because at least he was loyal and adequate to Xehanort, unlike them.
Eraqus
Some entirely new characters.
