Microsoft are most likely to release a new console at the end of 2013 with a reveal next year at some point, with Sony at most a year behind them. Maybe later, but 100% definitely not before then otherwise investors would have already been notified and dev studios wouldn't be flat out denying they have the dev kits. As for Nintendos Wii U it's already confirmed for a 2012 launch, probably end of 2012 since the games are so early in development and they'll want to release around Christmas.
The next gen wii is hardly rumoured, Nintendo themselves unveiled it at e3. It's called the Wii U. Sony and Microsoft have both point blank denied they're releasing any new consoles (other than vita) in the next two years and their projected earnings back them up.