Preview at WWDC likely in June, followed by September launch.
Apple Announces Dictation, iCloud Tabs, and 'Power Nap' Features in OS X Mountain Lion, Available in July for $19.99
The new dictation feature will be integrated throughout the operating system to allow dictation anywhere to enter text. Dictation was previously rumored in May when resource files in Safari listed keyboard shortcuts that pointed to dictation functions.
iCloud Tabs, a new feature in Safari on the Mac, was also demonstrated. iCloud Tabs will show all tabs open in Safari on all other iOS devices and Macs logged in to the same iCloud account. Safari also gains a unified search and address bar to streamline its interface.
Power Nap is a new feature that will carry out functions while a Mac is charging and sleeping. New emails will be downloaded, Time Machine will automatically run, app updates will be applied and other actions will be carried out with Power Nap, which will be available on the new ultra-thin MacBook Pro that was announced today and second-generation and later MacBook Airs.
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.