Halo 2: Anniversary has been scheduled for release on Tuesday May 12, 2020 at 2000h. After play testing the game, there were no show stopping bugs found. Some map problems were discovered and those will be fixed undoubtedly.
Halo 2 only took 6 months from the release of Reach suggesting the rest of the MCC collection will be as lethargic to be released. At this pace, MCC may not be complete this year.
Now that Halo 2 is available, this leaves Halo 3 as the next game to be released. Right now there is still a lot of work remaining for Halo 3 before it can be released. ODST is also being working on as is Halo 4.
Halo 5 is still a ways out before it can be found on the PC. Halo: Infinite is still 4-5 months away as well.
With Reach, CE and now Halo 2, the PC gaming community at least now has some more maps for multiplayer and more campaigns for those who like the action and story. Only god knows when the rest of the MCC collection will be ready.
343 said there was still a bunch of less important fixes to be handled soon. Of concern is the problems with an Ryzen R5 processor and Radeon graphics.
Halo 3 is now ready for debug flight testing. The internal testing should take a week or so to accomplish. Then flight 2 will take another week or so. Flight 3 will be the final stage before it is ready for release. This makes a June release a distinct possibility.