It may not be BlizzCon or QuakeCon (at least not yet), but the developers of the Civilization series and Xcom: Enemy Unknown are hosting a one-day event called Firaxicon in Hunt Valley, Maryland on September 27. The event is being pitched as an exclusive affair rather than the expansive conventions of the previously mentioned devs.
Firaxis are promising lots of activities including tournaments, a special presentation by Sid Meier, a visit to Firaxis Games and more.