It's looking like Valve may have quietly launched Source 2 in the latest Dota 2 update. While it appeared to be an update about the workshop and changes to the tools, users have noted that file paths and text within the schema all point to this being a soft launch of Source 2.http://www.lazygamer.net/general-news/has-valve-secretly-released-source-2/
L4D3? TF3? Dare I say.... HL3?