A job advertisement has revealed the first information regarding the next game in the Call of Duty series. It was revealed last week that Call of Duty 5 is on the way and now, via a Treyarch job advertisement, we have the first game information.
Despite the success of Call of Duty 4 and its modern setting, the setting for the fifth game looks set to be WWII once more. The Treyarch ad (developer of Call of Duty 3, Call of Duty 2: Big Red One, and Call of Duty: United Offensive) states the successful candidate will be working on an "industry leading First-Person Shooter action war franchise" and that it's beneficial to be a "fan of World War 2 shooters".
While this doesn't 100% confirm CoD5 will be a WWII shooter, it's a logical assumption to make.