Doom 4 has no set release date, that it'll get a release date when the developer is ready to release it. Essentially, "done when it's done."
Carmack did reveal that development on Doom 4 has intensified, as teams have been pulled off their own mobile projects to help out with the game.
"Essentially everybody will be focused on Doom 4," revealed Carmack, who then added, "I hope that we do get back to mobile in various ways in the future, but the real aim is blockbuster triple-A titles, and for Id that means Doom 4."
In other Doom news, Bethesda posted a new trailer for the bonus "Lost Missions" levels that will be included in Doom 3 BFG Edition, which is due to be released on PC, Xbox 360 and PlayStation 3 on the 16th October.