Preview at WWDC likely in June, followed by September launch.
Apple Seeds Fourth Beta of macOS High Sierra to Developers
The fourth beta of macOS High Sierra can be downloaded from the Apple Developer Center or over-the-air using the Software Update mechanism in the Mac App Store.
macOS High Sierra builds on features introduced in Sierra, focusing on new core storage, video, and graphics technology. It introduces a new Apple File System (APFS), High Efficiency Video Codec (HEVC), and an updated version of Metal with support for VR and external GPUs.
Some apps are gaining new features in macOS High Sierra. The Photos app is being updated with a new sidebar that's designed to make it easier to access editing tools and albums, and there are new filters and editing options like Curves and Selective Color. Photos also supports external editing apps like Photoshop and Pixelmator, saving changes made in those apps, and it interfaces with new third-party printing services.
Safari is gaining speed enhancements, an option to end autoplay video, and a new feature that puts a stop to data tracking. Siri in macOS High Sierra has expanded music capabilities and a new, more natural voice, and Spotlight supports flight status information. There are also improvements to iCloud, FaceTime, Messages, and Notes.
macOS High Sierra is available for both registered developers and public beta testers and will see several updates ahead of its expected fall public release.