ex-Valve veteran Tom Leonard confirms: he worked on Source 2 from Nov 2010 - Feb 2013

#5
Source pushed physics so far back in the day that I can't wait to see how they push things again. Hope to see fluid dynamics and cloth simulation next gen finally!
 
#14
We've known of the existence of Source 2 since 4chan's visit to Valve. Newell himself confirmed that they're working on Source 2 and that's it's a brand new engine instead of an update to the previous one.
 

JaseC

gave away the keys to the kingdom.
#18
I'd be happy if anything comes out in 2014/2015 at this point
Fun fact: If not released earlier, Episode Three/Half-Life 3 will become Valve's longest-gestating project on October 3rd, 2015 (judging from initial announcement -> release date).
 
#20
So, if my message board etiquette is correct, we should now be blaming this guy, and this guy alone for fucking up Source 2 and delaying HL3. Screw you, Tom Leonard!