I can see them purchasing a smaller developer like PlatinumGames, but the internet's been saying larger companies like Capcom or Sega, but I can't see a reason they would do that.
PG is not looking to be bought and they have well over 200 staff and currently have projects in development not for Switch. Nintendo would not neeed to buy them. They could invest in them. Once Sony had a 20% share in Square. Nintendo could do that. PG likes being independent. They don't need to be owned. Nintendo can do what they always have done as well. Just work closely with a studio. They don't own IS. They are just closely affiliated. Inseperable to the point they don't need to own them. Next Level Games and Hal labs are the same.