Preview at WWDC likely in June, followed by September launch.
OS X Mountain Lion Adding Offline Safari Reading List Mode and Dictation to Mac
Gear Live highlights the offline reading list option, which is an augmentation of the Safari bookmarking feature that debuted in OS X Lion and syncs saved articles across devices. As noticed by Gear Live, a warning screen in Safari on OS X Mountain Lion indicates that articles saved to Reading List are available for viewing even when the user's Mac is not connected to the Internet.
While troubleshooting a home network issue today, I stumbled upon a new feature that Apple is introducing in OS X Mountain Lion. [...]
When you aren't connected to a network and pull up Safari, you get a message that tells you that you aren't connected to the Internet, but that your "Reading List articles are available for viewing while you are offline."
Meanwhile, 9to5Mac reports that a keyboard shortcut listing in the latest build of OS X Mountain Lion suggests that built-in dictation capabilities will be coming to the Mac. Such capabilities debuted as part of Siri on the iPhone 4S, with only the dictation portion making its way into the third-generation iPad released earlier this year.
According to a resources file inside of the latest build of Safari in the newest seed of the upcoming OS X Mountain Lion, Dictation might be making its way to Macs next. Since Macs do not sport virtual keyboards or physical keyboards with a microphone-labled key, users (by default) will apparently need to simultaneously click both command keys to start voice input.
No other evidence of dictation or other Siri-like features has yet been discovered in OS X Mountain Lion, but Apple continues to work on the next-generation operating system and will undoubtedly issue an extensive preview of it at next month's Worldwide Developers Conference in San Francisco.