It’s not a stretch to say that the villain’s ultimate goal — and even the villains themselves — change in every Kingdom Hearts game.
There was the fairly simple fight between light and dark in the original, which changed to the more complicated machinations in Chain of Memories and Kingdom Hearts 2, with the inclusion of Nobodies and their individual goals plus Xehanort’s goal of remaking the universe.
Then Birth by Sleep shattered the relatively standard RPG trope of being god by including the X-Blade and Master Xehanort’s desire to remake the worlds, addressing an imbalance between light and dark. It featured, again, in Dream Drop Distance, but there’s yet to be any concrete discussion of why.
Granted, explanation doesn’t always happen in RPGs, but for a series spanning over a decade now, it seems unlikely it’ll end without delving deeper into the particulars.
Master Xehanort probably won’t be one of those misunderstood villains — he’s done too much bad for that — but the core idea of balancing light and dark has gradually become more prominent as the series has progressed, especially with Terra’s and Riku’s character arcs.
Hopefully, there’ll be some more world building and plot exposition on the subject to help explain what Master Xehanort originally wanted.