Late 2012 it'll launch. For all the profit they've made, Nintendo don't have the resources to support and launch a completely new handheld and home console inside of the same year. Their internal teams will be stretched enough as it is until the first wave of 3DS games are done, and until the last wave of Wii games are done. I don't doubt they're working on a successor, but I can't see them announcing a new home console for launch this year. They MIGHT announce a codename or something, at the most.
They have enough to compete with against Apple/Sony to make sure 3DS gets off to a successful start without worrying about launching a new home console. Plus, they're going to need to take their time to get third parties on board for their next home console, and part of that is doing whatever they can to see 3rd party success on 3DS.
