Team Fortress 2 team shares new improvements and changes of the Case System, coming with the Pyro update, which at the time of writing doesn’t have a specific release date. Main goal is to simplify the case-opening process, so it’s easy to determine the specific content that come out of cases and to add more value to the player each time a case is opened. Crates will not be affected by these changes.
The changes will be applied to all existing cases released from the Gun Mettle update forward. All cases will have a chance to receive bonus drops upon opening and will share a list of effects for the Unusual items received. The shared lists of Unusual effects and bonus drops will be cycled periodically to change the combinations of items being received in order to make room for special limited-time versions of the shared lists for holiday events.
For additional information and details, you can also check out the Official Page.