Nintendo Direct focused on Switch 2: Apr 2nd.
Looks like joy-cons will have 'mouse-like' functionality and there's a 'C' on right joy-con but its functionality is not reveled. New Mario Kart showcased would probably be one of the first exclusives.
Marketing will be difficult, MK8 already peaked graphically and has 96 tracks, and will still work on Switch 2. I hope they'll find real selling points for MK9.
I mean, at this point it makes little sense for them to start from scratch, releasing a newer game but with much less than the enormous amount of content provided by MK8D + DLC would seem like a very noticeable downgrade, so just revamping the old one would be a practical move, though I don't think fans would be happy with that.
MK8 was mostly flawless gameplay wise, how can it be improved? But at this point one has no choice but to trust Nintendo's ability to come up with surprises.
There are certainly some ways they can, I'd love to see a 100 man race or something crazy like that.
Mario Kart sells like hotcakes; I doubt they'll have to do much to convince people to buy a new one, particularly folks who've played the old one for hundreds of hours.