Mr Carmack was up on stage at QuakeCon last night, and he was talking Rage and PC. Getting the PC version up to speed has, apparently, been one of the sticking points for Rage's development, which has taken a few years now. Interestingly, release might not be the end of the that particular line of development, either, because Carmack has revealed that he's already started a new project, and the “research engines” that this new project produces could be added to the PC version of Rage down the line. Quite what this means isn't clear, but apparently he has a "firm" plan to release this update to PC, as well as a high-quality texture patch. It's fascinating to see Carmack getting excited about the PC again, a platform whose power he called "crazy". Increasingly, I suspect, the words out of the mouths of Carmack and other tech gurus are going to be about the untapped potential of the PC, particularly as the archaic specs of 360 and PS3 begin to frustrate those developers who are still interesting in pushing their technology. There's a bit more detail on Mr C's talk here.
I've also posted a big old Rage trailer below.