I've not been following any of the news surrounding Call of Duty recently, but I just took a survey through GamerInstincts and they asked my opinion on a upcoming synopsis to a game. Call of Duty: Lone Wolf. I wasn't able to copy paste the information, but the story seems to revolve around a single player tactical stealth game in which you must infiltrate a terrorist overrun nuclear reactor/missle base? PS3, 360 and PC That's a brief info from what i can remember before it kicked me out for trying to copy it. It sounds to me like Call of Duty is trying to switch tactics and go the route of Metal Gear Solid. Again, this may or may not be real, or it could just be a synopsis to interest the survey, but it still merits possible rumor notes.
That is how many people get ideas and see if they work. If the survey is successful then they might implement the idea. Though this is the early stages, there is a good chance they will ditch the idea.
I wouldn't mind it.. so long Infinity ward makes it. Unlike Treyarch, they know how to tell a story and game like that would need a story.