Not too excited about it...
Hardcore gamers probably won't buy many. It's the games that sell the console and 3rd party Nintendo developers have focused too much on the kiddies leaving most non-casual gamers to enjoy the PS3 and X-Box systems more.
Casual gamers aren't likely to buy it either. They will likely tell you that they already have a wii system that they almost never play.
I think people underestimate the graphics potential of what is in the Wii U system.
I DO know what that graphics chip can do though (The performance is roughly equal to an HD 4890 or 5830) and I KNOW it will have pretty good graphics. Better than the PS3 or X-Box 360 for sure. All games could be made to play in full 1080p instead of 720p like most PS3 and X-Box games.
I didn't expect the Wii to out sell the PS3 and XBox consoles. (Due to casual gamer purchases of course)
I also didn't expect the XBox to be a more popular option than the PS3 but that $600 price tag was too much for many gamers. Eventually the price came down and leveled the playing field a bit but it always seemed that plenty of people had xbox's while far less had PS3's...
For next gen it's hard to say who will come out on top.
I'd be surpised if Nintendo come out on top but they DO have the advantage of being the first to the market and will likely be the cheapest option.
XBox has some momentum as owners have seen the console become closer and closer to a media center. I think they should play on that an allow bluray playback and a (seperate if needed) TV Tuner that would allow the system to act like a TiVo system.
For PS3 they need to push for the same TiVo ability but may need to have some kind of tricks up it's sleve to compete with the Kinect ability that will likely come on the new XBox and Nintendo's (likely) much lower price tag.
Hard to say right now, at this point it's anybody's game!!