With macOS Catalina, iTunes will be renamed Music. I say "renamed" and not "replaced" because despite looking like a brand new app, Music.app still has iTunes' heritage:
Same old preferences window
Still uses web views for Apple Music's screens
iTunes Store is still available
Some things have improved though.
With Apple TV coming to Mac, TV shows and movies have a more logical place to go into than the user's Music directory
Finder takes over iDevice syncing
Hopefully we'll no longer have to quit Music.app when Xcode updates
I personally like having podcasts spun off into a separate app, since iTunes clobbered your Up Next queue when you started playing non-music media
Music.app weighs in under 100MB, not counting any system frameworks it may use. Memory usage is consistent with that of iTunes, but I'm already looking forward to what Music.app will look like in macOS 10.16.