Call of Duty 5 is not call of duty world at war. This is a common mistake by people that have played call of duty 4: modern warfare. If you were a true cod (Callof Duty) fan you would know that there are much more then just 5 games and that after 4 the next wouldn't always be 5.
Call of Duty 5 is rumored to be Call of Duty 5: Modern Warfare 2. This information however was given from mtv . I highly doubt that Activision would give this information to mtv and not release this information to show like G4 but i could see why they would with the masses watching mtv they would get lots of hype for the game. For now we hardcore gamers must sit on our hands and wait and see what the next cod game will be.