Does Nintendo have any plans to release Spider-Man or Ninja Turtles games for the switch?

The issue here isn't with Nintendo...  but the IP rights holders.

In regards to Spider-Man, Sony owns the IP...  so all new Spider-Man games will be Playstation exclusives, which renders the probability of seeing Spider-Man on a non-Playstation console to virtually ZERO.  Not even Disney (who owns the Marvel IP) can intervene on this whatsoever as they can't use Spiderman in their games unless it's for a Sony console.

As for Teenage Mutant Ninja Turtles, it's going to be more the decision of DotEmu (publisher), Tribute Games (developer) & Viacom (rights holder via Nickelodeon) if they wish to port their upcoming game, Teenage Mutant Ninja Turtles: Shredder's Revenge ( https://www.shredders-revenge.com/ ), to the Switch (or other consoles) after their PC release.  While nothing is officially announced beyond the PC version, it seems that console releases are being planned & with the game being relatively family-friendly & being a 4P multiplayer game...  OUTLOOK SEEMS GOOD for a Switch release in the future.

As for other games making to the Switch, it's most up to the developer & publisher (no so much as the rights holders) to determine if their game would be a good fit on the Switch & if it's worth the cost of development.

The devs behind the Scott Pilgrim game, which recently came to switch, are making a new old school beat em up style game called TMNT Shredder's Revenge. They haven't said what platforms it'll be on yet but I'd be surprised if its not on switch. As far as I know there's no upcoming marvel games on switch but maybe that'll change soon. 

don't forget Mario, they never forget to release Mario.....zzzzzzzzzzzzzz