Doom (2016)

John Carmack confirmed in August 2007 that Doom 4 was in the future plans of id Software. On May 7th, 2008, id announced that the development of Doom 4 had begun.

Doom 4 is being built on id Software's id Tech 5 game engine. Furthermore, John Carmack has stated that the game will have better graphics than Rage, but is targeted to run at a lower framerate of 30 frames per second. Id Software also intends to make Doom 4's multiplayer mode better than Doom 3's.

Speculation
It is possible that Doom 4 will be a remake of Doom II, or will otherwise be set on Earth. Todd Hollenshead, the CEO of id, has made a statement which arguably supports this speculation. The comment was as follows: "Doom is part of the id Software DNA and demands the greatest talent and brightest minds in the industry to bring the next installment of our flagship franchise to Earth".

(Yea but the comment "bring to Earth" also means bring to life). ;-)