After several patches Halo: The Master Chief Collection is now a far more accessible and enjoyable experience online, and as such developers Saber Interactive, Certain Affinity, Ruffian Games and 343 Industries (it's quite the collaboration) have started focusing on more than just bug fixing.
To be more precise they have released a server-side update and with it the SWAT playlist, with modes for Halo 2, Halo 2: Anniversary and Halo 4, has been activated. Furthermore Halo 3 SWAT will be added further down the line, and on the Halo Waypoint blog recent additions are explained in more detail:
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. See the details of these changes below:
• SWAT has returned as the featured playlist. It features a variety of game types from Halo 2: Anniversary, Halo 2 Classic, and Halo 4, and we're making additional investments to include Halo 3 in the game type rotation for a future update. As we roll out additional content updates, we'll be bringing other playlists back into the rotation - these include Halo: CE, Halo 4, Team Hardcore, and future featured playlists, such as Team Doubles, Team Snipers, and more. As we mentioned before launch, we'll be keeping an eye on voting data and player feedback to determine which playlists stay in the rotation.
• Updated the player count to 4v4 (6 minimum, 8 maximum) for the following playlists:
- Team Slayer
- Halo 2 Classic
- Halo 3
- Halo Championship Series
- SWAT
• Updated voting options across multiple playlists to improve the balance of appearance of BR-start and objective game types.
• Updated the "max party size" for Big Team Battle from 4-6, and the team is working on resolving issues that are affecting parties with 8 players. Once resolved, the max party size will return to 8.
• In a future update, the ranked Halo 2: Anniversary playlist will be moved to 4v4. For now, as the playlist contains a variety of mid-size maps, we'll be temporarily allowing both 4v4 and 5v5 matches, but have optimized the voting options for this player range. For example, you'll see less 5v5 Team Slayer BRs on Warlord and more voting options that are catered to the current player counts of 4v4 and 5v5 (8 minimum, 10 maximum). Additionally, you'll now be able to search as a party of 5. These changes are temporary until we turn ranking online for additional playlists.
• Our next content update is scheduled for early next week, and we'll provide additional details of what's included in the near future. We thank you for your continued feedback, patience, and support.