Kingdom Hearts 3 may have only just released, but that doesn't mean we're not already thinking about the future of the series.
Although the game as a whole was fantastic, that doesn't mean that it can't be improved in many ways. There's also a ton of content that would make the game even better, as well as fixing some things that were disappointing about the game.
Tetsuya Nomura has confirmed that DLC of some kind will be coming to the game, and I can't help but think that means a big "Final Mix" package will come along and introduce a ton of changes.
Previous games in the series have seen Final Mix re-releases, and they've all been pretty significant in terms of what they added to the game and how they changed some mechanics. Final Mix has even added staples for the franchise such as Critical Mode.
Kingdom Hearts 3 has ended up being pretty divisive for all that it does differently (and how it concluded things), so hopefully, a few changes and additions would result in a better package overall.
Since this talks about some of the endgame content for Kingdom Hearts 3, there are spoilers ahead!