These don't all necessarily refer to future Call of Duty games. The fact that all of these were registered makes it likely that Activision is securing domains for potential future projects, even before those projects exist in any form, to avoid having to pay domain squatters later. Or, one of these could be a real game, and the rest a clever smokescreen by Activision, to prevent us from knowing which is real. It would be smart on Activision's part to use at least one of these -- after all, they all have most of the same words as "Call of Duty: Modern Warfare," which we understand to have been rather successful.
Superannuation speculates that one of these could refer to Sledgehammer Games' new Call of Duty game, which kind of makes sense -- if it's apparently going to be a drastic change in genre, why not a more fantastic, futuristic setting?