As usual with its annual release cycle, the installer will offer users the chance to perform an in-place upgrade, safely retaining their documents and data while the underlying OS gets a tune-up.
In approximately 3-4 months, Apple will make macOS 10.15 (aka Catalina) available to the masses for download on the Mac App Store.
Why I'm buying the iPhone 13 Pro Max, and maybe you should, too.2021 event: What you need to know (free PDF)