The second beta of developer is now available to developers. iOS 12.3 (compilation 16F5129d) from macOS Mojave 10.14.5 (18F108f) of watchOS 5.2.1 (16U5091b) and tvOS 12.3 (16M5129d).
As we commented, the first test version of iOS 12.3 and tvOS brought the revamped Apple TV app.
These new builds of iOS, macOS, and tvOS should soon paint on the Apple Beta Software Program as well. And, as always, if more news comes, we'll inform you here. 😉
Update by Rafael Fischmann 04/09/2019 s 14:28
The new trial versions of iOS, macOS and tvOS are now also available to Apple Beta Software Program members.