With the 40th Anniversary of Mario this weekend, I'm curious what they'll do for that? Super Mario Wonder was only 2 years ago, so I don't think we see a brand new sidescroller so soon, the Super Mario Odyssey team made the new Donkey Kong, so probably no huge new 3D Mario, I can't think of a big collection they'd do other than maybe making a proper 3D Mario collection that has more improvements, includes Galaxy 2, and isn't freaking limited in its release, but that's mostly re-releasing a previous anniversary's bundle.
Maybe a remake? Super Mario World getting an Octopath Traveler style remake would be pretty fun, keeping the pixel art intact while adding some visual flair, or Super Mario 64 getting a big overhaul would be cool too. I'm just sorta throwing out random ideas as there's a lot they can do for it, though it's also Nintendo, and they'll often make decisions I don't like, such as their art style choice for the Link's Awakening remake lol