Oh, and as someone who has spent an egregious amount of money collectively on the 3DS version, Wii U bundle, another GameCube adapter, and the DLC characters and stages, I can't say I necessarily want an upgraded NX port from a consumer perspective. However, Super Smash Bros. is the only game I play regularly so I know I'd buy an NX port, and Nintendo knows I, and many others, would too in addition to all the people who couldn't be bothered to buy a Wii U for one game.
I really can't see Nintendo not doing this to strengthen NX and continue printing money.