This Facebook Page has artwork that fan site ValveTime believes is from Half-Life 2: Episode 3 circa 2008, saying: "These fantastic images have been sent in by an anonymous visitor to the site from an unknown source. Despite that, we have no reason to believe they aren't real. One could argue that perhaps they are just generic Half-Life 2 concept art of concepts that never made it into the final game. But there's plenty of evidence here to suggest they are post Episode 2." Computer and Video Games says they've reached out to Valve for comment.
Wallshadows wrote on Jun 27, 2012, 21:26: Has Valve ever given a reason as to why they hate making a third title in a series or is that just a fallacy created by fans?
Both.
edit: Err, originally a fan thing probably but now they probably playing into it.
Wallshadows wrote on Jun 27, 2012, 21:26: Has Valve ever given a reason as to why they hate making a third title in a series or is that just a fallacy created by fans?
Well... technically... EP2 is the third in the HL2 series. HL2, Ep1, Ep2.
I wouldn't call those images "fantastic". They look kinda slapped together and rushed. Mildly interesting, but not fantastic. I've seen much better stuff from first year art students.