Preview at WWDC likely in June, followed by September launch.
Apple Releases Second macOS Sierra Public Beta
Beta testers who have signed up for Apple's beta testing program will receive the macOS Sierra beta through the Software Update mechanism in the Mac App Store.
Those who want to be a part of Apple's beta testing program can sign up to participate through the beta testing website, which gives users access to both iOS and OS X betas.
macOS Sierra is a significant update that brings Siri to the Mac, allowing users to conduct voice searches to find files, look up information, and more. New Continuity features include an "Auto Unlock" option for unlocking a Mac with an Apple Watch, and a Universal Clipboard for copy paste that works across multiple devices.
Deeper iCloud integration makes files stored on the desktop or the Documents folder of a Mac available on all of a user's devices, and Photos features new deep learning algorithms for facial, object, and scene recognition. Messages includes rich links, bigger emoji, and "Tapback" response options, and the macOS Sierra update will bring Apple Pay to the web.
For full details on all of the new features included in macOS Sierra, make sure to check out our macOS Sierra roundup.