Mario 3D World is this year´s big Wii U game for the Holidays, we all know that, as for next year...DKC comes out in February, Mario Kart sometime in the first semester if I´m not mistaken (am I?), as much as I´ll (probably) enjoy Bayonetta 2 and X, I don´t think they´re 'system sellers'.
Or perhaps something quite surprising, that we´ll know about at E3 2014?
You are not mistaken, Mario KArt 8 is spring 2014, but all points out to april as the release month.
Bayonetta could be August, X will launch in Japan this year, but not in America, Nintendo just takes too much time to translate.
Looks like Smash could the holiday big tittle, but with Nintendo you'll never know, they could have something in the works from sometime (was is Intelligent systems doing, what is Intelligent Systems doing?, what is Nintendo EAD group 4 doing?, what is Headstrong games doing?), and of course they can have some kind of collaboration with a third party like Sega, Namco or Capcom that brings something else to the table.