ShackNews published some tidbits about Doom 4. The site heard the game may not be released as Doom 4, it's possible that id Software will give the fourth version of Doom a subtitle instead of a numeral, and that the game won't be a direct sequel to Doom 3.
However, id CEO Todd Hollenshead claims that a final judgment has yet to be made in the numeral versus subtitle debate. "We haven't made the decision about that yet," he told Kotaku. "There is probably a let's not make a numeral game and some say we should make it one."
Willits further noted that Doom 4 will not be a direct sequel to Doom 3, as Doom 3 reimagined the storyline of the original Doom, but refused to offer any additional details.
id Software says Doom 4 will use the id Tech 5 "Rage" engine but states it will look like it uses a totally new game engine because Doom 4 is targeted to run at 30FPS, whereas Rage shoots for 60FPS. John Carmack explains this allows id to throw three times as much horsepower at Doom 4.
The final snip of information about Doom 4 is that the game will have a much better multiplayer experience than Doom 3:
Saying the Doom 4 multiplayer experience will have a "much larger presence" than that found in the previous Doom title, the id president said that his company should have enough resources to create a satisfying online component to match the single player campaign.
"[Doom 4 multiplayer] will not be as good of a multiplayer as Quake Live is, but it should still be good, and we will intend it to be better than Doom 3 or Quake 4 multiplayer," said Carmack.