Preview at WWDC likely in June, followed by September launch.
Apple Seeds Golden Master of OS X Mountain Lion to Developers
"200 New Features" Mountain Lion slide shown at WWDC
Apple released the Golden Master (GM) version of OS X Mountain Lion to developers today. The "golden master" designation indicates that this version of the software is intended to be the final version released to the public, barring any last-minute issues. The Build is 12A269.
Apple first previewed Mountain Lion in February, highlighting many features already present in iOS, including Messages, Reminders, Notes, Notification Center, Game Center and more at that time. At WWDC, Apple announced additional features, including Dictation, iCloud Tabs, and 'Power Nap'.
We previously highlighted this video which shows off many of the new features found in Mountain Lion:
Mountain Lion will be priced at $19.99 and released to the Mac App Store in July.