I really hope not, I would like this story to more contained and not a massive foreshadow for the next game. I think the really cool thing about games like BBS was it was answering more questions than it was raising. It was immensely satisfying to play that game and see all the connections with other titles. By the end of the game, I felt like I really understood the larger story.
The story of KH is often seen as a joke, but when mysteries and answers are done correctly, man does it work really well. Xehanort and Braig I think are characters done really well when it comes to further developing them and making their additional context reveals work well. They are characters that keep on giving; just when you think you know everything, something else is revealed. Normally that would be annoying, and I'm sure it is for many fans, but I think each reveal has worked well in making more sense of their characters, especially when looking at past scenes. Knowing Braig is Luxu when watching all his past scenes is just fun because his character actions actually make a lot of sense.
I would like this game to work in a similar way; fill in details that fans have been wondering about for years (how Xehanort escaped Destiny Islands, who his master was, how his heart first went astray as mentioned by Yen Sid in BBS, etc.) and adding some additional context while not going crazy with random events meant to do nothing more than advertise the future of the series.