There has been news that this was coming for a while. Now they have provided a timeline, and it is coming soon - next month for many.
I think the comments on the article say it all. This is a terrible move. Google Play Music isn’t perfect, but way better than YouTube Music.
The worst part is that even after the app becomes completely useless to me, it will still be installed and not removable on my non-rooted phone. That kind of irks me.