Total War: Rome II will be getting an expansion, called Caesar in Gaul. This new campaign will focus around Caesar and the Gallic War, and the campaign will feature seasons with weather effects. New units will be added to the game, as well as the Nervii, Boii, and the Galatian factions.
This expansion will be out soon, on December 12th, for $14.99. Usually the expansions for Total War games have the best campaigns -- at least that's how it always seems to me -- so I am pleased to hear this.