50k? This would
VF5 sold in its first week only 50k on PS3 with the userbase of 660k. So i dont think it can 75k on smaller userbase. Especially thah if someone wanted VF5 he had his a half year to buy it and probably has it. Of course the online addition will help but not that much. Xbox 360 broke 50k only once when was released and I don't think it will happen again.
Also when you look how other consoles are doing 50k would be a good result not only for PS3 but even for Wii. For a console which sells 1.5k per week it seems much to high.