Switch might be ultra popular and its games are selling extremely well, but there have in fact been unusually few new Mario games released for it. Mario Kart 8 Deluxe is just a remastered version of the Wii U title, and Super Mario Odyssey remains the only brand new Mario adventure to the format.
But this doesn't mean Nintendo has forgotten about their plumber, quite the opposite. If the proven Nintendo insider Zippo is correct, there are actually several Mario games in development, with some being practically finished. In his blog, he asks himself "Where's The Next Mario Game?" and lists everything he knows.
It turns out we can look forward to two sports titles with Mario, one based on baseball and the other one on the Olympics. Paper Mario 2: The Thousand Year Door is also being remastered, and is almost finished already. Finally, there's a new 2D Mario adventure in development.
While none of this is confirmed in any way, and Nintendo is amongst the very few companies these days who can actually keep secrets, Zippo has still got plenty of things right in the past.