Honestly, looking at timelines I think it's likely Wii 2 will launch first (Wii fell in Japan in 2008 and hasn't really regained much ground since, and Nintendo always looks to their home market when planning launch cycles) and it may come as soon as Q4 2011. In terms of hardware spec, Wii 2 will likely be just a normal generational upgrade, meaning there won't be as much pressure on Sony & Microsoft to push to their next cycles right away. This will also likely benefit 3rd parties, as they'll now have 3 consoles to launch games across and share costs/risk with rather than just 2, though it might also result in the 3rd placer getting squeezed out GameCube-style as the gen goes on and Wii 2 gains ground. Like with 3DS vs PSP, you can probably also expect Wii 2 spec to be a decent increase over PS3/360 capability, and probably with a focus on developer ease of use.
Microsoft's timeline I think depends entirely on how Kinect fares though. They're in no hurry to rush the cycle, they've clearly shifted priority to profitability and MS PR has even espoused their own "10 year cycle" for 360. Xbox 3 will probably launch alongside PS4, the only way I can see it launching earlier is if Kinect utterly bombs and the current 360 market basically dries up next year, in which case a Q4 2012 launch might be possible. But that looks pretty unlikely imo.
