Apple released the first beta version of the upcoming macOS Sierra 10.12.6 update, developer-oriented and created for test purposes. It came out just the day after the release of macOS Sierra 10.12.5, which contains minor improvements like fixing a problem with USB headphones and supporting the installation of Windows 10 Creators Update via Boot Camp.
MacOS Sierra beta 10.12.6 is available for download from the Apple Developer Center by developers and through the Mac App Store update mechanism. It is not yet clear what changes are envisaged in macOS Sierra 10.12.6, since Apple did not disclose the details. It can only be assumed that this will be a small update, with an emphasis on "waggly" changes, increasing stability, productivity, correcting mistakes and shortcomings. As expected, macOS Sierra 10.12.6 will be one of the latest updates for macOS Sierra 10.12, while Apple will begin to transfer focus to macOS Sierra 10.13. The announcement of macOS Sierra 10.13 is to take place at a conference for developers WWDC 2017 (Apple Worldwide Developers Conference), which will be held in San Jose from June 5 to 9.