I presumed this would happen from the beginning but it sure took a long time. Android 9 finally has a feature to remember last used volume from connected Bluetooth devices. This means you no longer need A2DP Volume to manage the media volume for you (its original and primary feature). In fact, if you have Android 9 do not use the A2DP Volume media volume adjustment feature as it may fight with Android 9's own feature for this same purpose.
Here is an article explaining the Pie volume management feature: https://www.androidpolice.com/2018/08/07/android-p-will-remember-individual-volume-levels-bluetooth-device-connect/
Here is a brief statement about the feature: "Volume memory per Bluetooth device: Android 9 will now remember the last volume you set for each of your Bluetooth devices. No more blasting music too loudly when you reconnect to your car or headphones."
At this point A2DP Volume is an maintenance mode. I plan no new features for it and I expect over time it will quietly disappear as people get Android 9 and above.
See also issue 287: https://github.com/jroal/a2dpvolume/issues/287
