From Nothing But Shooters: "In regards to subsequent titles after MW2, it appears that Treyarch's next stab at the franchise may center on the Vietnam War with possible espionage missions based on The Cold War era, and I have previously suggested that Future Warfare would be received well, should it be the decided direction when the series inevitably shifts gears again.
But what about the Civil War? Would this be a viable course for the franchise at some point in the future?"