Do you really need sequels to Mario Kart and Smash if they add the original game + dlc + new characters/stages for this final mix. I think you are good. Let them release the older games via VC for added kicks.
Splatoon is a new IP, so the original game + and a later sequel make sense.
Yeah at some point, it feels like they don't need sequels. Nintendo is hitting a limit on graphics where they don't care to make it much better.
They can just do DLCs like you said, or make it F2P.
Splatoon probably deserves a sequel, but after that, it doesn't really.