I think the PS3 will benefit most from GTA4-
GTA fans will correlate Platstation Brandname and GTA... Kinda like if they released Halo 4 on PS3 and 360... it would sell 4x on the 360.
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