According to whom though?
Honestly, I think the average fan doesn't even know the difference between the CoD games... just like most of them didn't probably notice that Neversoft took over Guitar Hero. And hell, given that this will be based on the CoD4 engine, there's no reason that the average consumer doesn't just think this is a natural sequel.
I'm not saying that I wouldn't like to see IW take over CoD for good, but I just can't believe it. It would have to tank as much as Tony Hawk for them to do that, I would think.