They really don't need to at the moment. They have plenty of partners, the usual suspects (Intelligent Systems, Game Freak, Next Level Games, Monster, Platinum, Camelot, Grezzo, Tantalus, HAL, Sakurai, Creatures) plus new ones such as Mercury Steam, which I guess will be more than happy to keep working on 2D Metroid for them for the time being, given their success, or Ubisoft Milan, which clearly has a profound love for Nintendo and is without a doubt doubling down on their collaboration. Also, they are doing fine licensing their IPs to other medium sized Japanese publishers, such as Koei Tecmo (Hyrule/FE Warriors, Other M) and Namco Bandai (Smash, Pokken, F-Zero in the past), initiative that they probably want to extend to other pubs as well: they've already worked with Capcom on Zelda in the past, with Square on Super Mario RPG, I can see them working together again.
Besides, now they should concentrate on making the recently restructuring work well in first place and transfer their portable focused series to the big screen without hiccups.
Buy Rare back from Ms as that pirates game is probably going to bomb.
Rare of today =/= Rare of 15 years ago. Also, buying a company whose most ambitious game in years allegedly bombed, doesn't seem like a sound business decision.