I think the Wii U launch was fine, and they definitely shouldn't have waited a year. As has been said, launching a year earlier might have been a good idea, even at a high price like $399. Ease it in slow and capture people that were upgrading to PS360 from Wii. They also could have diverted Skyward Sword to Wii U.
But I think the launch was timed well. The botched it a little by announcing it too early. It dragged on for two years, reducing the hype. They also over-estimated the draw of NSMBU to the core gamers, those who would buy it early. NintendoLand is also a lame name for a game trying to lure the casual crowd. It needed Wii Sports U and a graphically stunning core title. Regardless, it doesn't matter. 360's launch was a disaster, but when you have no competition it's OK. The Wii U has a year to work out its bugs and build up its software library. Other next gen systems will be lucky to have 2 or 3 decent exclusives and will be at a higher price. Nintendo will be in a place where they will have 10-20 exclusives, a streamlined, updated OS, a decent install base and a couple of AAA must-have titles that have been in development for a long time. 3rd parties will also bring titles like Watch_Dogs over because it is financially sensible given the respectable install base. Nintendo could also drop the price if necessary, as manufacturing costs will have dropped after a year of optimization.
The only drawback I see at the moment is I think Nintendo expected other consoles to go with 4 gig RAM. They went with 8, which puts Wii U at a significantly greater dissadvantage, technically.