Just two days after releasing its last updates, the next round of Apple betas is now available. The new updates are iOS 12.4, macOS 10.14.6 Mojave, watchOS 5.3, tvOS 12.4. There's no official word about what's included in these builds, but there are likely some improvements made for Apple Card, which is coming soon.
iOS 12.3 and the updates that came alongside of it were midstream updates. These are pretty typical for Apple, and they're minor feature updates placed between major ones. You can expect these new updates to be more about fixes and improvements, with the odd new feature like Apple Card support.
If you want the big new features, that's coming at WWDC in a few weeks. On the first day of the conference, Apple will announce iOS 13, macOS 10.15, watchOS 6, and tvOS 13. Following the keynote, registered developers will be able to try out early betas, with public betas for everything except watchOS coming later on.
If you want to check out the first betas for iOS 12.4, macOS 10.14.6, watchOS 5.3, and tvOS 12.4, they're all available for registered developers now.