Half-Life: Alyx is out today, it's a great VR game and a great Half-Life game, and perhaps best of all we don't have to stop joking about "Half-Life 3 confirmed!" because neither that nor the semi-sequel-ish Half-Life 2: Episode Three are still nowhere in sight. In an interview with IGN, level designer Dario Casali explained why, after 13 years, a proper Half-Life sequel still hasn't happened.
Half-Life 2 took an unexpectedly long time to make, in part because it was developed alongside the Source engine it uses. "I think our main takeaway from that is, 'Get some stable technology and then build a game on top of it'," he said.
That resulted in the plan for episodic releases, which were intended to keep Valve from running silent for years on end: Instead, with the Source engine fully mature, episodes were planned to come out on a yearly basis. But then "scope creep" set in, as the developers kept cramming in more and more features. Casali said it was "a good concept," but one that Valve didn't execute very well.
13 years after Episode Two, a followup hasn't happened for two main reasons: One, a reluctance to, as Gabe Newell said in this separate IGN interview, "just crank Half-Life titles out because it helps us make the quarterly numbers," and two, and the creation of the Source 2 engine. Source 2 was officially unveiled in 2015 but Casali said that Valve was itching for a new engine by the time Episode Two rolled out—but it didn't want to repeat the "pain" of the Half-Life 2 development process.
The good news for long-suffering fans is that Casali said Valve has continued to work on various Half-Life projects over the years, it just hasn't come up with anything it's satisfied with. And while the VR-exclusive Half-Life: Alyx is out of the reach of the bulk of PC gamers, we can reasonably expect that more is on the way: Valve's Robin Walker said earlier this month that the studio sees Alyx "as our return to this world, not the end of it." That probably means we'll be updating our Half-Life 3 rumors, leaks, and hoaxes list again very soon.