It really shouldn't come out sooner than the next PS or XB, but that's not the issue.
Problem is that Nintendo will be forced to do so sooner than it probably expected to.
Last gen was one of a kind and probably lasted so long because 2 of the main players for the 3rd party community had no rush to release consoles when they still had to recoup from their losses even years after launch.
So, with no news of a new console, gamers had no option other than stick with 360 and PS3 for more than they anticipated aswell.
Wii U has none of the above: no 3rd party support; no consumer support.
Sales will go down fast after Zelda, not just because the main hitters will have arrived already but because Nintendo will decrease it's support in preparation of the new gen.
Sony and MS can afford to decrease support because of 3rd parties. When Nintendo does it... well, just look at how their release schedule for Wii was like in 2011 and 2012.
In 2011 they released Zelda and Wii Play 2. That was it. And in 2012... nothing.
How will they keep Wii U alive if the Wii situation repeats itself?
