Sure if they:
To Mario Kart, drop half the babies, add some actual new characters, fix battle mode, bring back the mission mode from DS. Maybe some new modes too.
To Smash, uh Story mode? that could be a thing, again more modes could help too, besides Smash Run and Tour (Tour not being that good) etc.
Some stuff like characters and stages/race tracks could be fixed with periodical updates, tho I doubt any of them would be free, then may as well make a new game with a lot of new stuff.
About Mario Maker, I can only see it work with the Switch if it has a touchscreen, otherwise it won't be nearly as fluid and intuitive as the Wii U game. They can still do 2D Mario games, which would benefit from Mario Maker existence, basically they would need to make one with new mechanics and power ups not found in previous titles to make it more appealing.
In the end, I don't find MK or Smash to be the ultimate titles of either series, they can still tweak many things on these games (MK8 pretty much being your typical MK game only with DLC, and Smash besides DLC still has lacking features compared to say Brawl).
