Nintendo won't be technologically behind this upcoming generation.
The Wii U will almost be as powerful as the next generation of Xbox, according to an IGN source.
The source claims that the next generation of Xbox will utilize a graphics processor that will provide 6 times the processing power of that of the Xbox 360. Compared to the Wii U, however, the new Xbox will only be 20% more powerful. This seems to point out that Nintendo is again going to provide us a system that isn't far off from its competition, much like the GameCube was in the previous generation. The gap between Nintendo's current system, The Wii, and other systems was quite large.
The Wii U is expected to make one final appearance at E3 2012 before the rumored fall 2012 launch. The next generation of Xbox is expected to launch in fall of 2013.