Game Informer had an interview with John Carmack about id Software's upcoming Rage game, the Tech 5 game engine and various other things. You can read the full interview over here.
One of the things Carmack said is that id is definitely planning a Doom 4, a new Quake Arena and a new Wolfenstein game:
Then you’ve got the run and gun internal shooter stuff, id’s always done well, and we’re going to do a good job on that. Then you have the sort of RPG-ish elements, pimping out your ride, getting money to buy accessories and building it up. It is a different style of game which is risky especially when you’re talking a $20 million budget, and the safe this for us to do would be to run right into Doom 4. But we made the conscious decision that we want to broaden id a little bit. We’ve got Wolfenstein, Doom, and Quake. We’re trying to bring Orcs and Elves up from the low end, and we’re going to try to bring Rage in from the high end to broaden our whole portfolio here. There’s no doubt it’s a gamble. It’s a big deal. There’s an element of stress there that we don’t have all of the advantages that we previously had going into a title, there. But we think it’s going to be pretty cool.
There will be a Doom 4, we don’t have it scheduled or a team assigned to it, but there will be a Doom 4. There’s going to be a Quake Arena sequel. There’s a Wolfenstein thing in production. We’re following along with all those. This game doesn’t have to be Doom. It’s going to be something different.