As of today, Activision had a Q4 Conference Call. Here they gave a presentation and have listed a "Call of Duty 2013".
Activision has confirmed this and stated: "The Call of Duty franchise continues to set the bar for innovation and we expect the new Call of Duty game in development for 2013 to raise that bar even higher."
As of now, Activision hasn't elaborated on who the developer Call of Duty 2013 will be at this time. What do you want to see from the next Call of Duty? Let us know in the comments!