It"s the nature of every all-you-can-eat subscription service to add and remove content over time. Adding new content regularly increases the value of a long-term subscription, and older content must be removed to avoid price increases. After all, the content must be licensed from the content owner.
With that in mind, Microsoft will be removing 21 games from its Xbox Game Pass service at the end of the month. Here"s what will be removed from the service on May 31 (via VG247):
Xbox 360
Age of Booty
The BioShock trilogy
de Blob 2
Borderlands
Dead Rising 2: Case Zero
NeoGeo Battle Coliseum
Dig Dug
SoulCalibur
Final Fight: Double Impact
SEGA Vintage Collection Golden Axe
Operation Flashpoint: Dragon Rising
Bionic Commando: Rearmed 2
Pac-Man Championship Edition DX
Bound by Flame
Sacred 3
SEGA Vintage Collection Alex Kidd & Co.
XCOM: Enemy Within
Xbox One
Defense Grid 2
Blood Bowl 2
The way that Xbox Game Pass typically works is that you can download a game from the service and play it for up to 30 days. You should be able to download any one of these games up until May 31, and still get a month of gameplay out of it. With that in mind, if you want to play one of these games before you have to buy it, you"re going to want to start soon.