Last month Microsoft announced that an upgraded version of Halo 3: ODST would be made available for Halo: The Master Chief Collection, along with the remastered version of the Relic map from Halo 2. Thanks to a leak posted over on Xboxdynasty, it has been revealed that it's scheduled for release this Friday, that's May 29.
The game is being promised to everyone who bought Halo: MCC between release and December 19 of last year, with the campaign a free offering to appease fans after the multiplayer side of the current-gen collection including Halo 1-4 was released in a completely broken state (it's much better now, thankfully), and since the leaked picture doesn't show us a price tag we still don't know what it will cost for the latecomers. Guess we'll find out on Friday.