I think it's a little premature to call the WiiU a failure. Sales got a nice bump from the lower price and WW bundle, and the big guns will start hitting in the next 6-12 months (3D Mario, Smash Bros., Mario Kart, etc.). Millions are just waiting for enough worthwhile games to be released before they pull the trigger on Wii U.
That being said, it's definitely destined to be a distant 3rd place this generation. They refuse to work with and give 3rd party developers what they need. Wii U just doesn't have the power and architecture to support easy ports, so unless something changes I think the Wii U will suffer a short life propped up mostly by flagship Nintendo titles. They did create new casual gamers with the Wii, but they now play on their phones instead of the next Wii system.
Their next system simply has to be built with 3rd party developers in mind, first and foremost, otherwise they're sadly going to go the way of Sega. Buying a Wii U is like buying a Blu-ray player that only plays Disney Blu-rays -- they are top notch and family-friendly, but sometimes I want to watch something more mature than Toy Story.