The Wii U is shaping up to be a disaster, but it's worth keeping in mind that the 3DS is more than fine, even if it's not up there with the original DS. And the Wii was a huge success (call it a fluke if you want, but it was still colossal for them). The GC was considered a disappointment, but still turned a healthy profit side-by-side with the GBA (which I believe was their most successful handheld). Nintendo is far from doomed, and they aren't as in much trouble as people seem to think. Even though they still the Wii U at a lose, it's been said to be a very small lose and that even a small amount of software sales can compensate.
The real blunder that Nintendo has made this gen was with the marketing, I think. Not only did they fail to sell the gamepad in the same way they did the original Wii's motion controls, just the way they named it (this was also the case, I think, with the 3DS to a lesser extent), and how they didn't change the logo even with the awful name. It's series of ideas that seems so basic, it's amazing that they passed through.