Disclaimer: This is in no way a complete list of things that are new, just an overview of the things I found interesting or was surprised to see!
MacOS 10.15 Beta
While this is a Developer Beta (only Registered Developers) that can only be downloaded by Apple Developer members I was surprised as hell that my 2012 Mac Book Pro is capable/allowed to get MacOS 10.15 Catalina. Every leak and report I have heard the last few months said that it would not be available on Pre-Retina Macs.
WatchOS 6 Beta
Again this is a Developer only Beta at this time but it should support all the LTE Apple Watches when it is Released Publicly. The greatest thing about WatchOS 6 is: No longer requires iPhone to update WatchOS (after WatchOS 6 Beta 1), includes it's own AppStore so you can now find/install/remove apps directly from your watch using WiFi or LTE (for smaller files), Apps like SleepWatch no longer require an iPhone to work - you can access the date directly from the watch.
iOS 13 Beta & iPadOS 13 Beta
Listing these together since technically they are still the same (at least they have the same Build Number). Only thing I can figure as to why they are now separate is due to the volume of devices Apple has in the wild or maybe the iPadOS version will have slightly different functionality on the larger devices than the iOS will have on the smaller devices. Either way I was stoked as hell to discover that contrary to every single rumor and leak iOS 13 will be available for the iPhone 6s and 6s+ (which I have a 6s I use for my watch and nothing else but no longer really need for the watch once WatchOS 6 Beta is installed! In both iOS 13 and iPadOS 13 we now, finally have DARK MODE, HUD for the Volume Controls (like AndroidOS has), an improved File Manager (with better external drive support) and a host of other new features and improvements!
*** If you are as excited for the new Apple Software as I am please let me know in the comments below and make sure you come Subscribe to my YouTube Channel (link below).