Modern Warfare 2, as is the company's pattern. And that's where David Kim's LinkedIn profile comes into play (check out his personal site here), which mentions that he's currently working as senior animator on Call of Duty 7.
With Modern Warfare 2 expected to deploy this holiday season, though, we likely won't hear anything substantial on this new Call of Duty for some time. But, considering how Activision likes to pump out the sequels to its key franchises, it's probably a safe bet to expect Call of Duty 7 sometime in 2010. We actually knew that before this listing popped up.