Soundwave on 04 February 2023
I don't think Nintendo will be launching with a 2D Mario again any time that soon after Wii U. It's not like NSMBU was a bad game, it's probably the best NSMB game by a fair margin.
Nintendo fans just tend to want an "epic" Nintendo game in the launch window. I think Mario Kart, Smash Bros., a new Zelda, big scale 3D Mario (ie: Galaxy or Odyssey or Mario 64) fit into that mold, or maybe you can double up like Mario Kart + Metroid Prime very quickly afterwards fills the gap.
