What do You prefer:

- Mario Kart 8 DX Odyssey DLC (2 new cups, 2 new battle stages, new characters like Cappy and Tiara) in few months

or

- Mario Kart 9 in 2-3 years

?

Super Smash Kart in 2 or 3 years.

MK8DX should not have existed, but since it does it should have been free for MK8 DLC owners.
I expect Smash to get the same deluxe treatment.

Honestly? I think that the core gameplay of MK8DX is fine enough, so unless they don't come out with a brand new idea for the franchise, I'd prefer that they keep updating MK8DX and focus their efforts in making new courses.

EDIT: D'oh, I feel that I'll be pretty alone in this XD.

Mario Kart 9, easily. MK8D is cool if you've never played it on Wii U (Or wanted a good battle mode), but I played the original (+DLC) a lot and I just want to move on to the next thing. I'm desperate for a new Mario Kart on the Switch =P

Mario Kart 8 is my favourite Mario Kart

I would like to see what new things they have to offer, so MK9

MK9

why split it up? Nintendo now has the hardware and software necessary to give their games DLC and season passes. I would absolutely love a single Mario Kart game filled to the brim with extra courses and features. There really isnt a need for another new game

Definitely MK9

If Nintendo wants my money, Mario Kart 9, still have 8 on my Wii U.