RTCW was released by id themselves last year, but maybe that was because Grey Matter (the studio that actually made the game for them) was defunct. Though it is interesting that the Enemy Territory source code was released when Splash Damage is still alive and kicking, though that was always a freeware title anyway. Still, it opens up the possibility for ET:QW in the future. As for getting the source code to Prey, an id Tech 4 title but not an id one, Human Head did release the full source code to Rune under the GPL, so that is not an impossibility either.
Still, all in all this has been a good year for source code releases. The Shadowgrounds and Shadowgrounds Survivor code are publicly available (albeit under a nom-commercial license, but still, you could make a source port if you desired) and now we have the code to Doom 3 as well. Last year we also got the original Humble Indie Bundle titles as well as RTCW and ET and of course Revenge of the Titans from the second Bundle. And Seven Kingdoms was freed up not too long ago. So we are not doing that badly.