The animated Mario movie is slated to drop on December 1, 2022. Who wants to bet a new (probably 2D) Mario game will be releasing next holiday season to coincide. I mean Nintendo would be stupid not to use the movie launch as marketing for a new Mario game.
I would say a new 3D game, but Switch has already got Odyssey and a bunch of old 3D Mario games, while we're still waiting for the Switch's first new 2D Mario game. Certainly enough time will have passed since Odyssey that they could have made a new 3D game, but the lack of 2D Mario is pretty obvious.
If BotW2 doesn't launch earlier in the year, that means Mario and Zelda is likely hitting holiday '22 season. That's gonna be a big sales season!