That's right, the next CoD has already been announced!

According to the original story that revealed the Black Ops name, the Treyarch-developed game will be set throughout the Cold War, and will feature key battles from across the period.

It will reportedly heavily feature segments from the Vietnam conflict - and culminate in the famous 1980 storming of the Iranian Embassy in London by the SAS.
http://www.computerandvideogames.com...VG-General-RSS

Of course, Treyarch will be developing it this time rather than the Infinity Ward team. I just hope that this will be worth of the Call of Duty name.