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".