Nobody bought COD 4 first week knowing how awesome it would be, they only had reviews tell them how awesome it was. That said it did over a million week 1 for the 360.
COD:WaW is releasing in the same time period, with great reviews and a MASSIVE fanbase. Unlike many other games COD4 sold on word of mouth because it was so good. So I think a lot of those fans will be eager to pick this one up. Not to mention since 4 another 10 million 360's have been sold.
I am only going to predict 360 first week but I reckon 1.6 mill







