In addition to the beta 2 version of macOS 10.14.4 released for developers a few minutes ago, the Cupertino company also released thes beta versions for iOS 12.2, watchOS 5.2, and tvOS 12.2. In these versions the first thing we can see is that bug fixes, improvements in system stability and security improvements are added.
As always Apple does not argue the news that are included in these beta versions for developers and therefore it is not clear if the new features implemented are the same as those of the previous version or there are changes. For the watch and for the Apple TV the changes are minimal and it is that they really work quite well in this latest official version released for everyone a few weeks ago, I would even say that smoother on older devices.
At first it seems that there are no notable changes in these versions so we continue with the novelty of AirPlay 2 on TVs, improvements to the Stock Market app for macOS and little else. Some news was also leaked in the version beta 1 for iOS with the arrival of "Hey Siri" for AirPods, but generally few notable changes.
So we will be pending until the developers get down to work and tell us if there is any news in the code of these new versions of macOS, iOS, tvOS and watchOS. Apple is also at that moment right now in which the important or most outstanding news will be saved to add in the June versions at WWDC, but they will not stop updating their versions with details on the overall security or stability of the OS.