Many of you may already know this but if you dont watch this video 
https://www.youtube.com/watch?v=HfYzPyJYXU0
Official confirmation or gtfo.
Oh, 6 minutes of you talking about things that have only been speculated about so far over a video of Lost Coast.
Ok.
This, this, this, this, this, and finally that show the evidence. This guy should have really just shown these links. The general opinion I think is that Valve is going to release some “Hybrid” source engine with the Left 4 Dead 2 port for Linux. Soon(-ish) after, they’ll announce Source 2. Presumably “Source Hybrid” will be an in-between for Source 1 content to Source 2’s engine. It’s speculated to be heavily OpenGL based I believe. Hammer will probably get a much needed update which means there will finally be a new moddable Source engine available.
And he disabled the voting on the video page because he got too many thumbs down.