Nintendo will release a new console late 2012 at the very earliest. Wii is following a similar trajectory to the PS2 (in fact is currently ahead of its sales curve) which had a 6 year life (as in 6 years before the PS3 was released) so I think Nintendo will follow a similar path.
2011 will be taken up by the 3DS, as well as a few big things for Wii like Zelda, and Nintendo isn't going to want another hardware release to crowd their lineup and deticate more funds. E3 2011 will be packed with 3DS info and demos, and possibly a teaser of the next Nintendo console.
2011 also holds more potential life for the Wii with games like Pikmin 3, Zelda, Last Story, Xenoblade, DQX, and the Vitality Sensor/Wii Relax. The console is also still only $50 cheaper then its original price, and Nintendo still has at least $100 in price cuts to use should the Wii begin to lose steam. There is really no reason for Nintendo to release a new console next year, especially when they already have a new handheld coming.
