Console hardware generations are measured by the time frame in which they were released and sold, not by the specifications.
Yes, the Wii was powered by updated 6th gen hardware with an all new UI, but it will still go down in history as Nintendo's 7th gen console, regardless of personal opinion.
The Wii U is the first of the 8th generation of consoles and no opinion is going to change that, regardless of the hardware specs.
I'm actually a little disappointed in some of the responses to this thread. I figured they'd be more along the lines of "it doesn't matter that Sony has sold more hardware than MS since the debut of the PS3; the generation is over/almost over/now irrelevant" but instead we're getting "why did it take so long" and the like.
In all fairness, it doesn't really matter whether the PS3 ends up selling more units than the 360 because the current generation is well past the point where hardware sales influence developer support. At this point, it really is just a matter of internet fanboys arguing over who was right years ago.
About the only thing either MS or SCE are concerned about are pulling whatever profits they can from fully matured hardware platforms before their successors take over in terms of market relevance (which may be another 1+ year past the next gen consoles' debut).
And for the record, it's more likely than not that the PS3 will match, if not exceed sales of the 360 when all is said and done which will mean nothing by the time that happens.