Develop has some excerpts from the Seven Day Cooldown podcast where Valve's Gabe Newell addresses the uncertain state of Half-Life 3, though he coyly calls the sequel he's hypothetically discussing Ricochet 2. The context makes it pretty apparent he's not actually discussing a sequel to this Valve created Half-Life modification, but rather the next full Half-Life game, though this is never explicitly stated. He uses this codename to explain the corner Valve has painted itself into at this point in terms of announcing and creating a third Half-Life (or second Ricochet, if you prefer). Here are the pertinent quotes:

“In terms of Ricochet 2, we always have this problem that when we talk about things too far in advance,” Newell said.

“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,” he said.