According to this report, Valve is working on a new game engine. Please feel free to make jokes about HL2:EP3 being released on the new engine.
Gabe Newell: We’ve been working on Valve’s new engine stuff for a while, we’re probably just [incomprehensible, subtitled as: "waiting for a game to roll it out with"]
Fan: Is it going to be more than just an extension to Source? Is it an entirely new engine?
Gabe Newell: Yeah!
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