We learnt late last year that Halo 3: ODST would be coming to the Master Chief Collection. This is in part due to the game's notorious connection issues, as the Halo 3 spin-off will be free to people who played the game before December 18th as that is when issues were at their worst.
Well 343 are going to make good on the promise now, as a listing seems to have outed that ODST will come to the collection this Friday. This was spotted by Destructoid who are saying that the game will be an 8.1 GB download. This could just be an admin error, but that seems unlikely.
We still haven't heard about a price to those who adopted the collection later on, but that will likely come tomorrow or Friday. I'm hoping for somewhere in the $10-15 range. That feels right.