This.  Quite a number of people bemoaned the decision of some developers to not bring their big budget franchises to the Wii U at launch suggesting some kind of conspiracy but porting games to a brand new piece of hardware is not always that quick and easy.  Some of these games have likely been in development for at least a couple of years at this stage and would be now in final development phase, focusing on optimisation etc.

Couple this with the Wii U's already relatively crowded launch window and the suggestion that 'final' Wii U dev kits have only been in the wild a few months and I can understand why some publishers have refrained from trying to port some of the generations most technically demanding games on an abbreviated timeline and on hardware that was, until quite recently, a moving target.