$300 or under and either a 3D Mario game or Zelda: BOTW at launch and I'm in.
I'm not too hung up on the portable aspect of it since I'll be playing it on a TV 95% of the time.
And I'm also being realistic about the graphics. Nintendo hasn't been in the business of releasing cutting-edge technology for the last 10 years so I don't think they're gonna suddenly start doing that again now.
I have a PS4 and a gaming quality PC, so I'd be buying this strictly for Nintendo games. I have the other systems for 3rd party stuff.