Halo: The Master Chief Collection is already pretty content-rich, containing Halo: Combat Evolved, Halo 2, Halo 3, Halo 4, the Halo ODST singleplayer campaign, and soon, Halo: Reach. The collection, in addition to giving players an easy way to access most of the franchise's classics, offers remastered visuals and improved matchmaking.
However, if that's not enough for you, the MCC is set to get even better moving forward. The official Halo Twitter account announced today that over 6.6 million user-created "Forge" maps and game types have been copied over from legacy titles (including Halo 3, Halo: Reach, and Halo 4) by developer 343 Industries, and will be made available in high-quality, remastered form in the future.
This massive user-generated map revival came about through the goodwill of both gamers and 343 Industries itself. Some time ago, the studio announced that it would be willing to initiate a "one-time" copy of any maps or game types fans were willing to upload from their Xbox 360 copies of the titles using a "file share" feature. It seems quite a few fans jumped on board, if that 6.6 million figure is anything to go by.
It's unclear when these maps will actually be made available for fans to enjoy, but it might be a while. Though 343 previously said PC players would be able to access these maps as well, none of the MCC's included games have actually launched on the platform yet (though the studio is making steady progress, with the help of beta testers).
Unless 343 splits up the maps' release across platform, we'll probably be waiting until at least the end of 2019 (the current target for the final release of the MCC's PC port).