Nah, he will stick to Square Enix at least until his beloved ideas for Versus XIII are reborn as Verum Rex, he can't let go of that obsession he has. No way he's leaving, unless there's a very important reason.
Even if he was to leave SE that wouldn't mean the end of KH. He could still collaborate with SE just like Nobuo Uematsu does. Or join Disney instead, they own KH after all (not a chance, I know).
I wouldn't believe any of this unless there's an official confirmation.