Yeah, however, leaks around this have been a bit more believable than before. Can’t remember the specifics, but more concrete stuff has been found by datamining (iirc) deadlock and paying attention to steamdb, with less reliable leaks ranging from the game or assets (again, iirc). So, there’s a fair chance this is real.

However, HL3 has been real multiple times before, it has been cancelled many times apparently, only to be taken up again later on.

Fact remains however, that Valve have been working continuously on an appid that isn’t deadlock for some time now, and there’s plenty of noise around them working on a new half life.