Iwata confirms remaster in the works!

[ToxicJosh]

I think Sunshine is most likely:

-Fills a 3D Mario slot
-Paint/water mechanics could utilise Splatoon engine (or vice versa, could Splatoon be an experiment derived from Sunshine remake?)
-Gamecube games not otherwise playable on Wii U
-Underappreciated at time (similar to WW)