I think they'll launch their next devices both in 2011, handheld and console alike. Wii's got a solid software lineup to take it through early 2011 (including potentially Pikmin, StarFox, and the Sora Project in 2011), and i think the end of that wave of software would be a good time to move on to the next console, without Wii having to go through another software drought. That way we could see a smooth transition between the consoles, and not like "the dead year" that GameCube went through before Wii came around
DS it seems like the same way, its on its last legs in terms of first-party software, even as it shatters records otherwise.
Monster Hunter: pissing me off since 2010.