Well, a big part of my reasoning for Wii2 at the end of 2011 is Japan. Even if it's their smallest market, Nintendo still makes decisions based first on the home front, and in Japan Wii's basically on life support. It's really past the point of needing a refresh (if that was going to happen, it should have already by now), Japan really needs Wii's successor. And in the west, even though it gets overblown, Wii really is on the backhalf of it's cycle too, and publisher support for the most part has already dropped out besides shovelware.
Strategically, if they can get everyone on board day one 3DS style (which, coming off this gen strong they'll actually have the leverage to do this time), I think they'd be in great position to hit the ground running and ensure market leadership for the next cycle. A big part of Wii's 3rd party problem was that no one expected it to lead (Nintendo included actually) and as such everyone sunk to much into 360 and PS3 R&D to just switch gears mid-stream. Wii 2 won't have that problem, it's going to be the assumed market leader going in, and as such will likely get a far, far better upfront priority from developers and publishers.
Another good indicator imo is EAD. For Wii, they basically only have one confirmed game next year, everything else is 3DS. This tells me Wii likely only has another year or so in the limelight, and you can probably expect any other EAD games to be shifted to 3DS or Wii 2 (similar to how GameCube "lost" Twilight Princess and Nintendogs). Get ready for Pikmin 3DS. ;)
My prediction is a Wii 2 unveiling at E3 2011, details as Gamescon/TGS 2011, release in Q4 2011/Q1 2012 worldwide.
