Update (Thu 6th Apr, 2023): Remedy Entertainment and Xbox's Aaron Greenberg have confirmed that Quantum Break will be returning to Xbox Game Pass, but it's being "temporarily removed" due to those aforementioned licensing issues.
"Don’t worry Quantum Break will be coming back to Game Pass. It is being temporarily removed due to some licenses that expired that were in the process of being renewed. Will let you know as soon as it is back."
That removal date is today, April 6th, with the game also having been delisted on the Xbox Store. There's no possible way to buy the game digitally for the time being, although hopefully it'll only be missing for a short period of time.
Original story (Tue 4th Apr, 2023): This past weekend, we were surprised to find that Quantum Break had entered the "Leaving Soon" section of the Xbox Game Pass library, suggesting that an Xbox first-party title was actually departing the service.
We were hoping to get more details from Microsoft as part of today's Xbox Game Pass roundup, but that didn't happen. Instead, it was just confirmed that seven games would be leaving on April 15th, with Quantum Break left in limbo.