Smash on 3DS probably won't hurt Wii U that bad. It's coming out earlier and I think we can all say more hardcore fans are on Wii U than 3DS. I honestly wouldn't be suprised if Smash was highest selling Wii U game once it's all said and done.
XBOX ONE/Wii U/3DS/PC
RIP Iwata 12/6/1959-7/11/2015
Thanks for all the great memories!