SteamDB recently changed how they scrape data from Valve's databases, and discovered that almost a month ago, an entry appeared for Half-Life 3. Or more accurately for Half Life 3, without the hyphen, which plays into this explanation of how not all of the entries in this DB are actually created by Valve, and that this may not be the confirmation it appears to be. They conclude: "TLDR: Half-Life 3 still not confirmed." Thanks DSOGaming.