If you check out Bethesda's blog these days, you're going to find out that id Software has publish a wide variety of job opportunities. Does that mean, they are working on a new title?

As far as quotes go, this one sais quite a lot: "id Software has a well-storied past, and now you can be part of their future". So far id Software is acutally looking for an environment concept artist as well as a design director.

If we combine this bit of news with the rumors, that Doom 4 should still be in development, then it could very well be, that id Software is recruiting for another successor of the franchise.

Source: www.vg247.com