Today, Apple released iOS 13.5 Developer Beta 4, along with new builds for iPadOS 13.5, watchOS 6.2.5, and tvOS 13.4.5. Both iOS 13.5 and iPadOS 13.5 were originally called version 13.4.5, until Developer Beta 3 last week when Apple introduced its new Exposure Notification API. Being that there's a new API, it needs a new SDK.
The Exposure Notification API is for COVID-19 contact tracing, and that's why the version number hasn't changed on watchOS or tvOS. It's not like people are walking around with their Apple TVs.
Aside from that, there are a few other key new features in iOS 13.5. It still won't let you set up Face ID with a mask on, but it won't make you wait a few seconds before entering a PIN anymore. Also, Apple made some changes to the way people are focused on in FaceTime calls.
The one new feature that was already going to happen before the coronavirus happened was the ability to share songs, albums, and playlists to Facebook and Instagram. These updates are expected to ship in May.