There may not be a Metroid or Castlevania game on the Nintendo Switch yet, but a Metroidvania game is on the way. Tom Happ, of Thomas Happ Games, has confirmed Axiom Verge is coming to the Nintendo Switch. In addition, a physical release is planned. (Thanks, World 1-1 Podcast!)
While a release window was unavailable, Happ did mention on the podcast what he hopes to include with each Axiom Verge retail copy. People would get the game on a cartridge, a manual, a documentary, and maybe a copy of the soundtrack.
Axiom Verge is available on the PlayStation 4, PlayStation Vita, Nintendo Wii U, Xbox One, and PC.