I've been thinking a lot about the rumored ports of MK8 and Smash Wii U coming to Switch, and the more I think about it the more I think it could be a fantastic idea if Nintendo treats them like platform titles and skips new iterations for Switch. Both Kart 8 and Smash Wii U were essentially designed to be the definitive versions of their franchise. Aside from giving them maybe a bit of a graphical boost when they get ported to Switch, there's really nothing that making a brand new successor to those games in the foreseeable future would add. They should just treat the upgraded ports as platform titles and gradually add new characters and tracks/stages over the system's life cycle. As for 2d Mario, Super Mario Maker essentially elimiated the need for Nintendo to ever make a new 2d Mario again, and as such this game should also just be ported over to Switch with maybe some gradual new content updates.
Now the biggest reason I think this could be so great for Nintendo is because it eliminates most of the dev time and resources for three of their biggest franchises and frees them to make more exciting and creative new IPs such as Splatoon. To me that game proved that people are craving new IPs from Nintendo, and when they actually get behind one it has all the potential in the world to reignite their brand. They've dealt with the learning curve of making HD games and have unified their platforms under one roof with the Switch. Now is the perfect time for them to begin a new era of Nintendo and introduce some long overdue new future iconic Nintendo IPs like Splatoon is sure to become. Take a break from Smash, Kart, and 2d Mario since the pinnacle of those series has pretty much been reached for the time being, and focus instead on new ideas and I think it could do wonders for Switch.