John Carmack states that Doom 4 will have "three times as much horsepower" tossed into it as it's running at just 30 FPS, compared to the 60 FPS of Rage. Maximum PC had a lot to ask the Doom creator, and he was fortunate enough to reveal some details.
We’re totally blazing fast because Rage is a 60Hz game. We want to be responsive for the driving side of things, and that carries over into a silky-smooth sense of play even with all the other first-person sides of things.Hopefully we'll all be able to actually see all of the eye candy the team is going to pump into Doom 4! Hey, if I didn't do a "Doom 3 is dark" joke here, I wouldn't be doing my job!
That also plays into our grand strategic plan with all this generation of technology. We’re ramping up to do another Doom game, built on id Tech 5. But it’s going to be a 30Hz game. Even though we’re not changing the engine, we get to throw three times as much horsepower at it, so it’s going to look like a totally new game engine on there, even though it’s going to be built on the four years of effort that we spent developing this generation of technology.