Either way I think it works in Nintendo's favor. If the competition doesn't show up until 2014 then the Wii U will have about two years without any competition, but if the competition shows up in 2013 then it will be so soon after the Wii U that the hardware couldn't possibly be much more powerful, while still giving the Wii U a year head start. So either way Nintendo will do well.
The only potential problem is if the 420 comes out EARLY in 2013 in like March or something, because then the Wii U's head start would only be a few months, and hardcore gamers would probably skip it in favor of that. But a 1st or 2nd quarter system launch has seldom ever worked well for anything, so who knows.
The PS4 may not appear until 2014, but we are already hearing so many rumors swirling about the 420 that it can't be that far off. So the Wii U will be 2012, the 420 will be 2013, and the PS4 will either be 2013 or 2014.