Alot of people went into KH3 expecting closure and i'm not saying they were wrong for assuming so but Nomura already stated KH3 wasn't the end of the series. Now i do agree there was more sequel baiting in KH3 then i would of liked. But i never expected to end KH3 without any lingering questions.
What questions hasn't been fully answered yet up to this point outside of UX/Verum Rex stuff which is clearly Phase 2??? Only one i can think of is the explanation of how Riku got Kairis keyblade in KH2. Most of the questions this series presents usually gets answered. It just gets answered at the same time the story presents new mysteries. Hell this is the same series that went out of it's way to explain why Mickey was Shirtless at the end of KH1, and created a entire mobile game just to explain how Malificent came back in KH2 lol.
As far as explaining who the foretellers are, That's already explained in back cover. The only parts of UX that needs recreating are the intro/parts of wreck it ralph and the ending. But yea even with all that u still looking at a solid 2 hours or so. It will be interesting to see how long the compilations will be once the ending is released and the youtube people packs the entire story into one video.
Nah they're going to have to explain and create a lot more than that. Namely:
1 Ventus being alive in UX and how he ended up with BBS with no memories whatsoever of his past memories. Chirithy knew him, but he had no idea himself of who chirithy is nor his past.
2.The nameless star (Sterlitza) being murdered by darkness who possessed the body of Ventus. Ventus in present day seems to have no recollection of those memories as well. They still also haven't explain the true identity of the darkness who killed her. If you never paid attention to UX, then you wouldn't have had an idea whatsoever of who she is/was.
3. They will also have to explain the identity of the traitor that was asked in Back Cover. They explained it in the game (likely Master Ava), but again you wouldn't know that if you never paid attention to the mobile game.
4. It should also be noted that certain members of Organization XIII and current characters appear in the game in their original forms. So they will have to explain to people what happened to them and how they are still alive in the game currently.
5. They're going to have to explain how all of those characters jumped into the present day story, while also explaining how Maleficent (who is alive during this time as well) managed to jump into the present day story also. It was already bad enough that they showed Ephemer in KH 3, which more than likely confused a lot of players who had no clue who he was.
That's one of the problems with adding/answering questions in the mobile games as it's going to take hours to fully explain it all.