This is the $1000 question. Google Play Music will live in the short term, but this comment from Google indicates that Google Play Music will eventually be retired - “it’s critical we have one offering that meets the needs of consumers and artists.”

Source - https://www.droid-life.com/2018/05/16/youtube-music-price-la...

Will YouTube Music launch with feature parity w/Google Play Music and offer an upload function so that users can stream tracks they upload themselves?