Mario Kart 8 Deluxe for Nintendo Switch has already outsold Mario Kart 8 on the Wii U.

In fact it's already sold more than Super Mario Kart, Mario Kart 64 and Double Dash. pic.twitter.com/SdTfHqaq00

— Daniel Ahmad (@ZhugeEX) April 26, 2018

Very impressive for just a port. :D

Sucks. My hopes and dreams are ruined.

It's not really surprising.
Considering sales of the previous entries it was quite clear that MK8 potential was capped by the WiiU.

20m is basically guaranteed by now, and 30m is a strong possibility if Nintendo doesn’t release a Mario Kart 9 on Switch.

Nope! Still got to waiy to see when mk9 releases. If its not announced by say end of 2019 then 20mil for sure. 30mil im not convinced yet (cuz of a possible mk9)

Well deserved, and its done that with minimal forced bundles.

If I were them I wouldn't release new MK on Switch, since they have that series covered they can focus on different franchises.
An alternative game would make more sense then a sequel, like Diddy Kong Racing (as someone suggested in the past).
Another option for them is to launch a strategic cross-over dlc when another major franchise hits the platform (like Pokemon).

Mario Kart didn't really get that big until DS, so outselling SMK,64 and DD doesn't really mean much to me. Great that 8 is selling well because it's the best Mario Kart game yet and it was a shame it's sales were so limited by the WiiU originally.

Good... 20 million for the deluxe alone will be impressive.

Talking about potential Mario Kart 9, with so great sales of MK8D Nintendo will not be in hurry to release MK9 on Switch, but would be great to see Diddy Kong Racing 2 in any case. :)