It was confirmed today on Inside Xbox That the MCC is coming to PC and that Halo Reach will be added to it on both PC and Xbox with 4k support.

To this day I still play the original Halo multiplayer on PC, so I'm very excited about this and having the potential to play those old familiar maps with more than the 60-odd people who have stuck with it since 2003. I just finished a Reach replay, so I'm okay with letting that one cool for a while.

Probably in an effort to not release a buggy mess, they are releasing the games one at a time, starting with Reach and going chronological order from there.