The franchise moved from the PS2 to PS3,so I'm sorry for the people that are underrating the game's potential to move hardware.
Fable II moved 360 hardware by 10%,the game releasing in America only,now GoW has a much bigger fan base than Fable,and the game is releasing in both America and Europe in the same week,and also GoW III is looking to be even bigger than Fable II.
So i would expect a hardware boost around 20-40%.
So...75k-100k is looking to be the highest boost it can get.