JayDee__ already posted the link in the comment in this thread but i think it deserves its own topic and a bit attention:

eurogamers interview: John Carmack's vision for the next Quake

although he confirms that they are not working on anything, he sharers some interesting information

"We are at least tossing around the possibilities of going back to the bizarre, mixed up Cthulhu-ish Quake 1 world and rebooting that direction."

"I looked at the original Quake as this random thing, because we really didn't have our act together very well.

"But because it was so seminal about the 3D world and the internet gaming, it's imprinted on so many people. It made such an impact in so many ways. Memory cuts us a lot of slack."

"Adding his thoughts into the mix, id CEO Todd Hollenshead said: "People shouldn't worry that we're ever going to orphan or abandon Quake. We are huge fans of the game internally."