This weird obsession with trying to shoehorn everything Nintendo does as "last gen" is asinine. There's more to the technology of video games than just the number of polygons being pushed or pixels being rendered or CPU power.
The Wii was part of the PS360 gen, period. It was the industry leader that introduced revolutionary control schemes and forced Sony and Microsoft to scramble to play catch up with the technological innovation that was actually driving sales through most of the generation (hint: it wasn't processing power). It was a different approach, a different KIND of generational leap, but a generational leap none the less.
The Wii U is a generational leap beyond that, taking those innovations for the Wii, catching up to the PS360 in terms of raw horsepower under the hood, and introducing more new concepts that might or might not be revolutionary, most notably TV-independent console gaming. Whether or not it's going to be an industry leader like its predecessor remains to be seen (I'm guessing likely not, but we still don't know much of anything about its competition at the moment).
Just because Nintendo is making different kinds of technological advancements than their competitors doesn't mean they are not making generational advancements.