Google says before the end of the year. I think it was announced last month as they announced you'd be able to migrate GPM playlists to YTM.is that confirmed?
How to transfer Google Play Music library to YouTube Music
Now that Google Play Music is shutting down, we tell you how to transfer your Google Play Music library and preferences to YouTube Music.
www.androidauthority.com
I'll probably end up waiting until the last days to see if they fix my issues w/ YTM.