So Half-Life: Alyx is an interquel taking place between Half-Life1 and 2, while Freeman is still in stasis?
That's my understanding (haven't played it since I'm miles away from being able to afford any kind of VR), but I have watched a few 'let's play' type vids (and thus seen the big reveals at the end). It doesn't really advance the HL story or timeline at all.
unless you consider un-killing Eli and having Stella Gordon get her groove his crowbar back "advancing the timeline". Really just altering the timeline, and not even in a way the necessarily says "we're definitely making HL3," since they could have easily done that and still had Eli deaded. Having G-Man be the prisoner was a really cool, if somewhat predictable twist though.
Still, looks really really cool, and I wish I had the setup to play it...but honestly by the time I can afford a VR rig to do it justice, there will probably be a billion other things on my play queue and I'll never get around to it.