id Software and Bethesda have updated the RAGE official website with a new release date, moving up the previous September 13, 2011 release date up by a month, to October 4, 2011.
GameStop has likewise updated their listing of the game to reflect the new date, giving further credence to the delay of the game's release.
The game may have been postponed to receive further polish, although there's a good chance that the release of Gears of War 3 may have scared them off a bit.