Ramping the new Source 2.0 engine to take simultaneous advantage of all three operating systems could easily have taken several years and is the likely driver of the delay, particularly if Valve wants to have new titles ready to go when it finally pulls the trigger on the new engine. At the same time, we've seen Valve expand its coverage into the Mac world - another significant investment of resources. But consider the timelines: Windows 8 began to pop up on the radar a few years ago, and Gaben's vituperous dislike of the OS drove him to create his own Linux distribution in response to ill-considered fears about Microsoft locking down the PC gaming world. In two years, we haven't seen hide nor hair of a new engine from Valve, though it was hinted that we might see such a project with Steam Box. The other slides hint at new development tools and environments coming down the chain as well and the screenshot itself is about on par for a high-end DX11 engine, particularly one built in the 2011 era (the slides are several years old).

Obviously this could be a 3D mockup or a faked screenshot, but the news (leaked by Valvetime forum member CBOAT) comes from someone with a long history of accurate releases and valid leaked information.

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