Well, the exact totals are anyone's guess, but it's VERY unlikely that the Wii won't win this generation. I know PS3 fans will mention MGS, GT5, KZ2, and whatnot, but get real, Nintendo also has plenty of tricks left up its sleeves.
I'd say Wii has 90% chance of winning, PS3 7% and 360 has 3% chance of getting first.
Estimates:
Wii 85 - 110 million
PS3 60 - 75 million
360 50 - 65 million