from http://kotaku.com/5031779/doom-4-to-use-3x-the-horsepower-of-rage-run-at-30-fps

Some interesting new news at Shacknews:http://www.shacknews.com/featuredarticle.x?id=956

During an interview with Shacknews, id Software president John Carmack described Doom 4 as being "significantly different" than Doom 3.
When asked whether the game will be rooted in the horror genre, Carmack indicated that it will instead focus more on pure action elements a la Doom 2.

Oh, man I don't know. I mean... Doom 3 was so freaking scary and just fear-crippling. I'd love for them to do something similar with Doom 4. I understand what he means by pure action elements. I would also love a full-blown shotgun-blasting experience with a big "fuck you" to the portal to hell rather than a more ambience driven Doom title. I just hope for a couple things:

1. The weapon sounds (especially the shotgun) is way louder and sounds a helluva a lot more powerful.
2. Another way to use the flashlight. I didn't find the switching to be a problem, hell, it's what helped the atmosphere, but it would make more sense to have a dim-light head flashlight or a small flashlight on your gun. A good way to keep the ambience without the game screaming FLASHLIGHT HEADLIGHT FJSLDFJSLFGJSL.
 3. For the love of god, make the Doomguy fire and reload the goddamn shotgun faster! Not only that, but give him a melee attack for his weapon.
4. They should really look into an Earth wasteland Doom game. Like, they could do a "right before the invasion of Earth" Doom 4, but they could also do a "20 years later ruined Earth" Doom 4.

Either way, I'm so excited to see what Carmack and others will do with the Doom franchise. No Doom game has yet to disappoint.