I don't know how they separate teams at SE, but I would rather XVI have a long development cycle and stay in concept stage for a while until they really nail it. The development process behind 15 was a mess and I really want them to focus on the FF7 remakes. I have many criticisms of FF7 remake, but it is my favorite SE game ever released. I really want the second and third (or how ever many more) to be even better in terms of dialogue and cutting out filler. While I generally hate alternative timelines and cyclical storytelling I actually think they did it in the most interesting way possible. I'm still worried that it will be handled poorly given the KH director being behind it and how that series has fallen apart to my tastes. I also don't want to run into a situation where voice actors age too much or can't fulfill the same roles for other reasons. It's pretty jarring to me in games when sequels have different voice actors. So I want the remakes to be polished, but I also want them to be the main focus of the studio and release in a timeline that isn't too dragged out.
Hot take: I have many thoughts on Kingdom Hearts all the way back from when Kingdom Hearts 2 disappointed me and nearly everyone I knew in real life; I'm on the side of the IGN review everyone wants to complain about, but even more so because the story bothered me back then and was already a mess as far as I'm concerned where the IGN criticisms are all about gameplay. The KH games still always have some redeemable qualities, and I did like KH2 but I think it deserved a much worse meteoritic score compared to the first. However, I'm most interested in FF7 remake sequels followed by FFXVI.
FFXV was kind of a mess in its own right despite having a ton of themes that I not only found interesting but even paralleled thoughts I had on writing my own fantasy novel. I didn't finish the game, but I've watched many videos on it because I was curious on why I didn't like it and what I was missing out on. It's development budget was rushed into production and they started to lose money before it was ready and thus we are left with a game that is divisive. The same can be said about XIII, KH3, and all games that overlapped its development. I want them to take things slow and not put a ton of money into XVI until they have the concepts nailed down completely and a plan in place. Until then put the main focus in FF7 remakes with the KH team doing its own thing.