Valve said last month that it was "confident" Half-Life: Alyx (opens in new tab) would not be delayed past its targeted March release, and that seems to be the case: It announced today that the VR Half-Life 2 prequel will be out on March 23.
Half-Life: Alyx, available March 23, 2020 https://t.co/NCOLWqSp3e pic.twitter.com/Q04EZwNfBtFebruary 13, 2020
The Steam page (opens in new tab) still lists it as just March 2020, but that's the official Valve Twitter feed, folks, so I'd say that makes it solid. Valve also dropped a trio of screens that I think are new—I don't remember seeing them previously, at least.
And for those who you who have purchased Valve Index VR rigs, preorder bonuses will start going out during the week of March 2, beginning with Steam VR Home environments inspired by Half-Life: Alyx locations. More information on the availability of the Index and related hardware (which are still out of stock across the board) will be announced "soon (opens in new tab)."