Although 343 Industries is keeping the release dates of the upcoming Halo: The Master Chief Collection, which will roll out game by game, down low, it seems one of the third-party studios helping in the port's development isn't so secretive. According to a newsletter sent by Splash Damage today -caught by a user on Reddit - the entire collection is slated to launch in 2019.
We already know Halo: Reach will be the first game from the bunch to arrive at PC, followed by Halo: Combat Evolved and progressing through the series in chronological order. But this is the first time we have seen a release window the developers are aiming at, which 343 has been putting as "ready when they're ready."
The newsletter reads "Halo: Reach is coming first, with the rest of the titles scheduled throughout the year." See here to have a look at the full newsletter. Of course, we will have to wait until Microsoft or 343 comes out and confirms the timeframe to make it official, but this coming from a co-developer should amount to something.
343 Industries is currently signing up participants for its new Halo Insider Program on PC, with those who are selected gaining entry into "early access play sessions with in-development Halo games." The studio also hosted a Reddit AMA recently where it answered community questions regarding the Halo: The Master Chief Collection PC version, which is coming to Microsoft Store and Steam.