The update cycle for Apple's new systems beta was running fairly regularly until two weeks ago, but from then on, everything went awry. Well, not that much of a problem it's strange to note that Ma just released a first beta of iOS 13.1 (build 17A5821e) and the iPadOS 13.1 (same build), which should only happen after the arrival of iOS / iPadOS 13.
The case could simply be a naming mistake: the first beta of iOS 13.1 should be the ninth test version of iOS 13, but no. The fact that, so far, the system is available for upgrade under this name.
In addition to the dawn above, Apple has just released the ninth beta version of watchOS 6 (build 17R5575a) and the eighth test version of the tvOS 13 (17J5564c). Also available was the seventh beta version of Xcode 11 (11M392r). No news so far about a possible new beta version of macOS Catalina 10.15.
Let's follow this story closely, remembering that, so far, the new test versions are available only to developers; iOS / iPadOS and tvOS should have their new public beta released in the next few hours / days (watchOS does not participate in the public testing program) in the Apple Beta Software Program.