Why wait for an official announcement from Bethesda or id about DLC for Rage, when a game ratings board in Europe will do it for them? PEGI (Pan European Game Information) recently listed a Rage game called The Scorchers, which has not been announced nor confirmed by Bethesda.
The Scorchers are supposedly one of the clans in Rage that landed on the cutting room floor. Your guess is as good as ours. We'll just have to wait until Bethesda confirms or denies the truth of the listing.