Call of Duty Black Ops is one of the staple Call of Duty Games. Honestly, look at it. Other than Advanced Warfare, it is the only to have three distinct iterations. People loved it and they still do, even though Black Ops III was just released a few months ago. It is possible that Microsoft acknowledges the love, because it is possible it is coming to the Backwards Compatibility program.
Spanish Xbox One news site Solo Xbox One released images of Call of Duty: Black Ops DLC being installed to their Xbox One; more specifically it is the Annihilation Pack 3. It isn’t uncommon for users to get “Ready to Install” notifications for unannounced games when close to official release. Since Microsoft has nixed the monthly release plan, it is possible it can be released in the coming week(s).
Keep in mind, none of this is official. All we have is the picture seen below, and the track record of random situations (including Age of Booty last month). Reports show Tekken Tag Tournament 2 has also appeared in some download queues, however there is no photo evidence that could be found.