Disclaimer: Rich Geldreich has explicitly stated that these views are his own and not reflective of the company (Valve) or its views.

OpenGL is the man behind the curtains in any Linux and most non-windows based Machines; that includes "Steam OS" as well. What Mr. Rich believes is very interesting, he states that Mantle and D3D12 are going to "thoroughly leave OpenGL behind". Now while that may be a mild concern for most Linux owners, this is very big news for SteamOS and its future.

'Rage' running in OpenGL Renderer.

"Mantle/D3D12 are going to most likely eat OpenGL for lunch soon" - Steam OS in Jeopardy

I am not going to treat this particular interview as an opinion for multiple reasons. This guy is the same person who wrote the first deferred renderer for the original Shrek game. Not only that but he has been in this industry for more than a decade working for high profile projects like Dota 2 and Portal 2. If the credentials aren't enough, he has listed somewhere around 26 highly quantified technical reasons why OpenGL needs to reboot. If it fails to do so it will most likely perish in the shadow of the giants that are Mantle and D3D12.