Finally, what can we say about the plot and setting? Treyarch have indicated it's likely to carry on the plot - which seemed to indicate (spoiler!) that Mason had assassinated JFK and Castro. Also, sound designer Collin Ayers has hinted on Twitter that the Zombies mode will be returning. Beyond that, we know very little.
While Treyarch is working on BLOPS2, both Infinity Ward and Sledgehammer Games are recruiting staff for new Call of Dutys. As Activision doesn't usually follow Ubisoft in having multiple studios working on a single title, we assume they're working on separate titles. Sledgehammer's support work on MW3 came about when Infinity Ward was depopulated by the departure of Jason West and Vince Zampella, but Activision will want the studio up to full speed in time for the next gen.
Hirshberg has promised "meaningful innovation" in the next 'all-new' Call of Duty game. November 2013 would be the next deadline for Infinity Ward, and that almost certainly puts it on shelves alongside a new Xbox and Playstation - so expect a new engine and an all-new story. West and Zampella have claimed ownership of the Modern Warfare name and they'll have their game in court this year, so don't bank on Activision calling Infinity Ward's next game Modern Warfare 4, even if they win. The name may have been dragged through too much mud by late 2013 for anyone to want it.
Lost in space
Sledgehammer is a new studio formed in 2009 from EA's Visceral Games staff, who previously worked on Dead Space. The rumour mill has their new game set in space in the far future, but that was apparently abandoned when they partnered with Infinity Ward in 2010. The other rumour about the Sledgehammer game is that it's not an first-person shooter but a CoD-branded action-adventure. But with MW3 finished, they've restarted work on their own title - and there have been no reports of redundancies there, which is the usual sign of a cancelled project.
Beyond that, rumours of an MMO are still circulating, but there are more aborted MMOs in publishers' archives than there are any other type of game, so don't count on it until you're playing it. Those rumours might even be related to the free-to-play Call of Duty that Bobby Kotick announced last year. It's a play for the massive Chinese gaming market much like EA's Need for Speed World, and it's unlikely Activision will ever throw it into competition with their western games.
CoD is expanding on five fronts - Infinity Ward, Treyarch, Sledgehammer, Elite and free-to-play - and doesn't look like doing a Guitar Hero any time soon. Try as they might, Activision can't quite run this one into the ground. Chances are you'll be called to duty for a long time yet.