I've posted this before and got shat on all over by Rol and Viper. The Wii was not even considered next gen by its own leader (Hiroshi Yamauchi), so this is no surprise to me.
Gens are rooted in the concept of technical advancements requiring changes to a console, things that could not be done before. That isn't the case for the WiiU, wasn't the case for the Wii.