Well, here's my guesses...
It's strength will be somewhere between Portable Ops and Metal Gear Solid on the PS, so we're looking at something like 240-280k, 'least that'd be my guess.
After that, the second week would probably be no higher than 70k, and the PS3's hardware saleswould have a high week when it launches, but quickly drop to sub-30k levels. I'd put holiday sales for MGS4 at 5k a week.
Lifetime, I'd put it at 550k or so.