"As the team continues to work on additional improvements to matchmaking and other areas, we are deploying a variety of server-side updates to matchmaking player counts, as well as bringing back SWAT as the featured playlist," the forum post explains.
SWAT includes game types from Halo 2: Anniversary, Halo 2 Classic and Halo 4. Halo 3 will enter the rotation in a future update. Developers also increased player count and expanded voting options in several playlists. Another update is scheduled for "early next week."
Halo: The Master Chief Collection, which corrals Halos 1-4 on a single disc, launched on Xbox One Nov. 11. Multiplayer problems have plagued the product since launch. Developer 343 Industries apologized in late November and pledged to "make it right."