Can't see Nintendo showing a new home console at the next E3, so that would rule out a 2011 release. I'd expect E3 2012 to be when they show their next home console, but I doubt that would be for a worldwide holiday release - the Wii will probably continue to do very well around Christmas for the next few years, and releasing a new console during such a period would damage that. Japan might see a 2012 release if Wii hardware sales all but dry up there, but I think a spring/summer 2013 release is most likely for the rest of the world. There are still a lot of titles that would sell in the millions that I expect to see on the Wii at some point (Mario Golf and Tennis, Starfox, Luigi's Mansion 2, PilotWiings) - even if third parties continue to keep their AAA stuff for the HD consoles, Nintendo's offerings alone should be enough to sustain decent hardware sales for another two holidays after this one, and I'm sure Nintendo want to milk the Wii for all it can before releasing the next system.
On top of that, I'm sure Nintendo can afford a couple of significant price drops between now and the next console. I expect it to drop to £130 at some point next year and the mass-market £99 price point the year after. I don't think the PS2 hit its sales peak until it was at one of those two price points, so Wii sales could seriously spike when its price hits those points.
