Prediction: You're wrong.

Nintendo likes money.

Mario Kart 9 is being developed right now as you're reading this post. 

I don't know, I can easily see MK9 around 2020.

No way, OP. There's always been a new Mario Kart game on Nintendo platforms since the SNES. It would be a big mistake to not make a new one for the Switch.

I don't think so.

And that's not splitting the community?

Which would make it about a decade after MK8, unless you think Switch is having a 4 year life cycle or less. 

Then every new console generation is a community split for you? OK. I just don't want that to happen during one console generation. I didn't even liked the moment valve announced L4D2 shortly after L4D1. 

But to be honest, even DLC can split the community, because you have the people playing only the vanilla version and the people playing the DLC one. It's annoying, but this is what happens. I also see DLC as a smaller investment compared to a MK9 full game release.

It does feel like MK has little elsewhere to go in its traditional format. 8 pretty much maximized it. Where could they go from here? Diddy Kong Racing 2. Of course Mario has far more brand recognition than Diddy does, so they'll call it MK9 or some offshoot. ~3 years from now, one can hope. There's my big prediction for the day.

A decade is too long between mk releases,mk9 probably will be released in 2018-2020

Surly new MK is in production as we speak. I'd say anywhere from three to five years from now. Probably by the end of switch's lifespan.