The sequel to the world's most popular franchise will depict the "world in chaos" after events in Modern Warfare 2 eventually put the US and Russia at dagger-throats. According to Kotaku, the game will feature the return of series regulars Soap and Captain Price.
Scale will be Modern Warfare 3's big evolution, with the action taking place on a much larger scale. Kotaku states that the game will feature "large, urban destructible environments". It sounds a bit like Battlefield, actually.
More details on Modern Warfare 3 are expected to be released at this year's E3.