While Apple has provided no detail on when the launch date [for macOS Catalina] might be, text on Apple’s Danish macOS Catalina website suggests that it could be coming on Friday, October 4…
An Apple Arcade section of the macOS Catalina website for Denmark says that Apple Arcade will be available in the App Store starting on October 4. The text is on the macOS Catalina page and refers to the Mac App Store… Apple Arcade on the Mac requires the macOS Catalina update and is a macOS Catalina feature.
MacDailyNews Take: Of course, as Clover notes, Apple could also release macOS Catalina earlier and then launch Apple Arcade on the Mac App Store on October 4th.
In any case, get ready for macOS Catalina!