Valve has never said that Half-Life 3 is a work in progress or even on the to-do list, much to chagrin and anger of Half-Life fans. There is still no official word on the matter, but Gabe Newell seems to have dropped a few hints in a recent podcast interview with the Seven Day Cooldown.
The podcasters asked for a status update on Ricochet 2—believed to be the codename for Half-Life 3—which provoked a laugh AND a response from Newell.
In terms of Ricochet 2, we always have this problem that when we talk about things too far in advance. We end up changing our minds as we're going through and developing stuff, so as we're thinking through the giant story arc which is Ricochet 2, you might get to a point where you're saying something is surprising us in a positive way and something is surprising us in a negative way, and, you know, we'd like to be super transparent about the future of Ricochet 2.
The problem is, we think that the twists and turns that we're going through would probably drive people more crazy than just being silent about it, until we can be very crisp about what's happening next.
It is highly unlikely that Valve is really working on a sequel of Ricochet, but his discussion of the status of Ricochet 2 is most likely the best news anyone is going to get on Half-Life 3.
In other words, be patient young paduwon. Half-Life 3 will appear when Valve is good and ready to discuss it. I'm calling 2015 release window in the office pool.
