iOS 13.1 beta 4 is now available to registered developers and public beta testers. If you're a registered dev or you're enrolled in Apple's public beta software program, you can download iOS 13.1 beta 4 over the air on your iOS device.
The update to iOS 13.1 is expected to bring with it some features that were announced as part of iOS 13 earlier this year but are now mussing from the iOS 13 update. These include Shortcut Automations and Share ETA with Apple Maps.
Also coming with iOS 13.1 are updates to Dynamic Wallpapers, more HomeKit icons in the Home app, and new AirPods, Beats headphones, and HomePod icons on the volume indicator. Apple has improved mouse support in iOS 13.1 as well.
Apple has said that iOS 13 will launch to the public on September 19, aka tomorrow. The iOS 13.1 update won't be far behind, rolling out to everyone on September 30.