Well, one thing's for sure - I won't be buying Splatoon until after E3 to make sure it's not coming to NX.
I already own Smash and Mario Maker, and I'm not sure if I could bring myself to rebuy them again for full price. Smash... maybe.
For Smash, there would need to be some hook. The game already looks great at 1080p/60fps, so it would need to be something like one of the following:
-Better character models (this is very possible, as presumably the models as originally developed would be much higher quality before being scaled down for LoD etc.)
-New characters / stages (less likely, but Nintendo have to know that it would help sell copies)
-A new multiplayer mode, or rejigged Classic mode (this is the one thing that would do it for me. single player in smash wii u was pretty terrible)
-New music, trophies and other side content (very likely)
Pretty much all my Wii U games are digital, so I'd love if they gave us some discount, but I can't see how they could possibly do that without utterly enraging physical buyers.