UPDATE (5/27): 343 has stated that the “May 29th” release date for Halo 3: ODST, that appeared on the Xbox Store, was a placeholder. They’re currently in the final testing phase.
“A placeholder release date for the ODST campaign for Halo: The Master Chief Collection was inadvertently listed on the Xbox Store. We continue final testing and will make an official announcement once our release date is determined, and apologize for any confusion.”
Halo 3: ODST for Halo: The Master Chief Collection has surfaced in the Xbox Store! 8.1GB in size and releases May 29th! The posting has since been removed. I assume the remastered multiplayer map Remnant (Relic) for Halo 2 Anniversary will also arrive the same day.
Halo 3: ODST’s campaign (not including firefight) is coming to Xbox One and will run at 1080p and 60 fps. Those who played Halo: The Master Chief Collection between launch and December 19th 2014 will receive it for free as compensation for the game’s launch troubles. There is currently no word if this DLC will be available for purchase separately at this time.
Halo 2 Anniversary’s multiplayer map Remnant (Relic) will be free for everyone, regardless when you played Halo: The Master Chief Collection.
Bonnie Ross apologized for the state of matchmaking for Halo MCC at launch and details about the compensation have now been announced.
To those who played Halo MCC online since launch, Nov 11th 2014 and through December 19th 2014 you will receive the following for free as compensation
1 Month of Xbox Live Gold
Exclusive In-Game Nameplate
And an Exclusive In-Game Avatar
As well as
Halo 3: ODST’s Campaign which will be playable through to Halo: The Master Chief Collection and upgraded to 1080p and 60fps.
And Relic, another remastered map for Halo 2 Anniversary from Certain Affinity. Bringing the total to 7 remastered maps.
Halo 3 ODST’s Campaign and the remastered map Relic are currently in development and are set for a spring 2015 release. 343 have stated it is just the campaign for ODST and they have no current plans to include firefight.
The remastered Halo 2 Anniversary map Relic will available to all users regardless of eligibility.
The 1 month of Xbox Live gold will be delivered to your account as early as mid-January 2015. The exclusive in-game nameplate and avatar will be available in an upcoming content update this December 2014. 343 stated the avatar and nameplate will not be available to additional users in the future. They also do not have any details at this time if they plan to have ODST’s Campaign available for purchase in the future.