Civ IV Expansion

The Civ 4 expansion has been announced, Warlords will be out this summer.

"An all-new expansion pack, Warlords pays homage to some of history's greatest military leaders, delivering six new scenarios, giving players the chance to change the course of history with the help of their new powerful "warlord" unit. The expansion pack is loaded with new civilizations, new leaders and more units, resources and wonders that can be used in both single and multiplayer games."
- from the press release here