We finally get a target date of when Google Play Music will be shuttered. The shutdown will start in Australia and New Zealand in September, with the rest of the world following a month after. Users won't be able to stream from the app and the web by then. But you can still transfer out music and data from the service until December 2020, whether you import it to YouTube Music or use Google's Takeout tool to retrieve your music uploads and purchases. After December, the data will be purged.
Google also plans to take out music from the Play Store completely, so you will no longer be able to buy songs and albums from the company directly. This change will come in "late August."
Source: Engadget