The axe is swinging around Xbox at the moment, as hundreds of jobs have already been cut across Microsoft's game studios. Of the teams impacted, id Software's reportedly been substantially hit, to the point that there's apparently only one single person left working on the id Tech engine.
This comes from a report by Kotaku which goes into the changes at the legendary studio. Sources tell the outlet that id Tech is now a department of one following the latest redundancies. The engine is bespoke technology to the company and has been the backbone of the Quake, Wolfenstein and Doom games since the mid-'90s.