343 Industries said in a forum post on Jan. 17 that beta testing for Halo: Combat Evolved Anniversary on PC would begin in February 2020, suggesting a full release is very soon.

Beta testing for Halo: Combat Evolved Anniversary on PC will begin next month, 343 Industries said in a forum message on Friday. The beta test comes a little later than anticipated, and requires an invitation to participate.
Though there is no formal sign-up, 343 developers gave out the steps for players interested in participating: Have an up-to-date Halo Insider profile with a verified email; opt-in for 343 to contact you; opt-in for PC flighting (343s term for a beta) and have your latest DXDIAG uploaded to your profile.
This flighting will be a limited content run involving multiple areas of the game, 343 said. The studio is looking to test out peer-to-peer connections cross-play among Steam and Windows 10 players, a new user interface for customization, and dedicated server validation.
For PC, 343 Industries is rolling out all the games of Halo: The Master Chief Collectionpiecemeal. Its proceeding in chronological narrative order, beginning with Halo: Reach in December. Next up is Halo: Combat Evolved Anniversary, with no announced release date yet. The Xbox One already has all six games the four numbered Halos, plus Reach and Halo 3: ODST in remastered form.