It is still way to early to make any big predictions about long term sales performance of the Wii U, but it is fairly safe to say that the Wii U will not be a "failure" in the way you're talking about ...
In the United States the Wii U is selling at 88% of the rate of the Wii, 140% of the rate of the XBox 360, and 275% of the rate of the PS3 after 2 weeks; in Europe we will have to wait for a few weeks to see whether the low sales were lack of supply or demand; and we have yet to see sales numbers from Japan.
In the coming weeks, I suspect we're going to see the Wii U sell at a rate that is halfway between the PS3/XBox 360 and the Wii which can hardly be called "failure" territory; and (in many ways) that is because the Wii U falls somewhere between those strategies. The Wii U is more expensive than the Wii was, with a less exciting controller, greater support from third party publishers, an earlier release date, and (potentially) less of a graphical disadvantage over Sony/Microsoft's next generation platforms.







