how do you know what WiiU can do? did any other console before Wii have motion controls?
The only way you can argue that Wii was next gen using the definition I gave is by considering the affordability of the parts used in the Wii (the argument is almost identical for the U).
Otherwise, the Wii is as much next gen as if you took an N64 with no analog stick and added an analog stick, in that the innovation didn't require technical advancements that were out of reach, only something that required thought and enginuity, and the idea. That's not next gen imho.