I doubt sales will fall THAT much based on the press. One of the big factors will easily be that gamers have formed communities and communicate with each other good titles. And even then the CoD franchise has enough behind it that it's got a strong backing already
This is kind of a shot to the guts of reviewers out there though, saying that they're extremely biased and would lower a games score, no matter how good it is, because of who made it. While a few reviewers out there could, I doubt that's what's on the minds of reviewers when they're playing the game.
Would you, if you were a reviewer, if you were playing a perfect game made by a company that had gone through what the CoD franchise had, mark it down from 100 to 95 because it wasn't the original company? If I'm not mistaken, FO3 and NV were made by diff. comps than the original few, and reviewers didn't look down on it. Diff. scenario technically but still
CoD:BO will do as well as it's designed and how well it plays. If it's shit, the scores will read shit, if it's good, the scores will read so. And fuck, it's gotten so much hype after what's happened with IW and Activision that I'm sure the sales will be fine, but if they are down it would most likely be because people want to wait and buy used so they can give their money to gamestop and the retailers and not Activision and it's prick CEO