Valve voice actor John Patrick Lowrie has announced via his blog that he has not worked on Half-Life 3, and later went on to say it currently is not in development. While not an official announcement from Valve, this is perhaps the most reliable source to date.
Stepping back, Half-Life 2 was released in 2004 to critical acclaim, igniting gamers with its cinematic-free storytelling style and crazy fun/surreal story. Half-Life 2 Episode 1 and Episode 2 were then released in 2006 and 2007, respectively, as sequels continuing where Half-Life 2 ended. Since 2007, fans have been waiting for an answer, for any tidbit of news on Half-Life 3.
Lowrie provided miscellaneous voices to the Half-Life series and he has his own ideas on Valve’s reasons for holding back on development. According to Lowrie:
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.
Let’s just hope the technology is here soon, so we can continue this crazy adventure.