Rage represents a rather large milestone for Carmack's id team. Not only is it the first game to use id Tech 4, it's the first id game to be published by new owner Bethesda. It's also the first new IP from the team in over a decade, since 1996's release of Quake. If a recent interview in the Official PlayStation Magazine (via CVG) is to be believed, it's likely that the new new IP from id will be just as far away.
"I doubt we're going to do another IP," Carmack told OPM. "We want to support Wolfenstein, Doom and Quake -- and hopefully we can add Rage onto that. ... Obviously, if Rage is a success then we'll want to do a Rage 2." Considering the lengthy development cycles at id (evidenced by the currently-MIA Doom 4) who knows when the next new IP will bubble out of the company?
Especially with that Commander Keen reboot getting in the way, right?