John Lowrie, a voice actor who has worked on several Valve games including DOTA 2, Left 4 Dead, Half Life 2 and Team Fortress 2, claims that one of the reasons Half Life 3 isn't out yet is because Valve is waiting for better motion capture technology.
Why Half Life 3 Has Not Been Released Yet
Here is the biggest challenge with bringing out HL3: the big thing now with FPSs is motion capture, or mo-cap. One of the great things about HL2 is that all of the characters that you meet actually look at you when they talk to you no matter where you go or stand. With mo-cap you can't do that, at least not yet. Once you film the actor doing something and capture that motion, that's what the character is going to do. This works great in movies, but when you make something interactive it gets way less interactive with mo-cap. So that's one of the things they're working on. Still nothing definitive, but I hope this helps you understand at least one of the reasons why they haven't brought out HL3 yet
John says:
August 14, 2013 at 2:02 pm
Right. As far as I know they are not developing HL3 now for several reasons, among them the mo-cap issue. Sorry for any confusion. What they might decide in the future depends on lots of different factors. I hope they do, personally, but it has to make sense for them.