MacRumors reports that Apple seeded the golden master version of macOS 10.15 Catalina to developers

The golden master version of macOS Catalina represents the final version of the update that will be provided to the public at release. The new macOS Catalina software can be downloaded using the Software Update mechanism in System Preferences after installing the proper profile from the Developer Center.

macOS Catalina eliminates the iTunes app, splitting it into Music, Podcasts, and TV apps. The three new apps offer similar functionality to iTunes, but are split up by feature. iOS device management is still available on the Mac, but it's now done through the Finder rather than iTunes.

  Apple Seeds macOS Catalina Golden Master to Developers