I mean...they really only Initially released MK 8 deluxe on the switch as an early on method of filling a gap in game release schedules and probably weren’t necessarily anticipating it would become the Systems biggest seller...and game development takes a few years. So it’s possible, in fact highly probable they have been working on mk8 successor to some capacity for a few years now. So it’s possible in my mind that we’ll see an mk9 sooner rather than later.
Supposing that is true and the game is good. The wise thing to do would be to sit on it until the Switch successor comes out.