Looks like Left 4 Dead 3 running on Source 2 is coming

Looks like Left 4 Dead 3 and the Source 2 engine may have been confirmed in a quite unusual way. During a tour of Valve to get a sneak look of The International 3, a member of the Dots 2 sub Reddit took a photo that shows a change log with Left 4 Dead 3 and Source 2 mentioned. You can see the zoomed in version below. 20130810-235013.jpg

Unfortunately  those of us hoping for news on a new addition to Half-Life will have to keep waiting, but hopefully with the development of Source 2 it could happen soon.