It's a possibility. SE seems to be supporting the Switch just fine, but with graphical less powerful games. So it's kind of up in the air. We'll see closer to release date maybe.
It's possible since kh3 isn't a PlayStation exclusive, it's already being release on Xbox one too, and squarenix is working with Nintendo a lot now, plus the fact that they've had some other kh on Nintendo consoles in the past. Fingers crossed tho