ioi actually did not undertrack the Wii at all... NPD did... ioi adjusted to NDP last week only to have Nintendo back up his original numbers.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut