I'm thinking 2011, which is what the Square-Enix president has said as well (maybe even summer 2011).
I think Nintendo will wait and see how the Sonywand and Natal are received first and will want to really one up that, not just throwing out some version of the Wii with HD graphics.
There is a chance you may see DS2 next year, maybe for Japan only at first though.
My guess is summer-fall 2011 Wii 2 will come out, but Nintendo will continue to sell the old Wii for a couple more years past that. Maybe even redesigning it to be even smaller/more cost efficient. Apple still sells the basic "vanilla" clickwheel iPod model next to the fancy schmancy touchscreen model.
Hardware revisions are actually good business too, especially if the hardware is profitable to begin with.
