According to a recent post on in September 2012 Bethesda has added a number of internal projects in the Steam catalog (Content Description Record). Including one called "ID Software Beta" in a package. Including the long overdue idTech 5 Software Development Kit, also known as id Studio, Doom 4, and a mysterious app called Project Ranger - suspected Quake 5.

Ranger is the main character of the 1996 original Quake.

Now its confirmed that Doom 3 BFG and Doom 4 for pc will be linked over steam.

original german news:

CDR: ID Software Beta -
CDR: Doom 4 -
CDR: Project Ranger -