If true, that would edge out Treyarch (which made the 3rd numbered game in the series) after they complete work on the CoD game that they're unofficially working on. With as much love as IW put into the excellent CoD 4, we can totally understand why they don't want Uncle Treyarch to babysit the series every other weekend. But, as we've pointed out, this is just hearsay at the moment. We'll let you know if we hear something official.
Update: Activision has responded, describing the rumor as "erroneous information regarding the CoD franchise."