The Master Chief Collection, 343 Industries' compilation of Halo remasters, has made it to PC bit by bit—after Halo 3 in July, on September 22 it's time for Halo 3: ODST, as the official twitter feed announced today.
With the Steam page stating that all games currently not yet available in the collection will be out "later in 2020", it stands to reason Halo 4 will be released before the year is out. It seemed like 343's goal was to have the MCC feature-complete on PC before the release of Halo Infinite, but that game has now been delayed into 2021.
ODST has always been sort of the odd one out in the series, with a noir-inspired soundtrack and a sidestory campaign that avoids the usual galactic scale of Master Chief's adventures. But it's also really good, and includes the fan favorite version of Firefight, the endless defend-against-waves-of-AI co-op mode, which is coming to the Master Chief Collection as well.
The Master Chief Collection supports a number of PC-specific improvements, such as variable framerates, ultrawide support and customisable key bindings. Additionally, 343 Industries is working on a number of new features, including crossplay, which will come to the collection this year.