According to Sony, the Android 6.0 Marshmallow will be available soon for the following devices:
1. Xperia Z3, Xperia Z3 Compact
2. Xperia Z5 Compact, Xperia Z5
3. Xperia Z5 Premium
4. Xperia Z3 Tablet Compact
5. Xperia Z2, Xperia Z2 Tablet
6. Xperia M5
7. Xperia M4 Aqua
8. Xperia C4
9. Xperia Z4 Tablet
Sony hasn’t made an official announcement about when these devices will receive the latest Android OS OTA update.
The Android 6.0 Marshmallow comes with many new features such as App Standby Mode and Doze which will improve the battery life of your device. When you will install an application, you will be able to choose which features the application can access and which can not.
However, in 2016 there will be more and more devices that will update to Android 6.0 Marshmallow, as long as they are powerful enough to handle it.