The desire we have to have a second beta of macOS Sierra does not prevent us from seeing the next beta versions of the operating systems that we have today. The fourth beta of OS X El Capitan for developers has been released at the same time as the iOS 9.3.3 and tvOS 9.2.2 betas.
As in previous versions of the operating system for our beloved Macs, little or nothing added apart from the improvements in system performance and troubleshooting small bugs or errors from the previous beta version released by Apple.
In this case it is true a week since the launch of the previous beta 3 of OS X and the rest of the systems, and we are clear that Apple will continue with this pace for at least two more versions until officially launching OS X El Capitan 10.11.6 for everyone. In reality few new features are expected in these versions and that is Most of the improvements are added in macOS 10.12 Sierra.
As always when dealing with beta versions the advice is to stay away from them and not install them at least on our main partition. Also in this case they are versions of developers and we have no doubt that it is not worth carrying out the installation on our Mac either.