It should remain dominant overall.
While 360 and PS3 are doing well now, this is because of price cuts, redesigns, and updated control methods. Move, so far, has had a relatively flat level of pre-orders and doesn't look like it's going to have much of an impact. Kinect is faring better, but I still don't see it having "life-extending" abilities.
The Wii, on the other hand, hasn't had any redesigns and only one 50 dollar price cut, and yet it is still on par with the PS3 in terms of weekly sales. By next year, it will still be going strong while the PS3 and 360 will sink back to their pre-price cut/pre-redesign level of sales. Plus let's consider that Nintendo also has the option to cut the price, release new control methods, or redesign the console.
In fact, I think the only reasonable threat to Wii will be Wii 2. If Nintendo decides to jump the gun and move upmarket with their next console, the 360 and PS3 may become irrelevant (and since they are planning on 10-year life-cycles they will be caught completely off guard).
