Preview at WWDC likely in June, followed by September launch.
Apple Scales Back Marketing Language on OS X Security Following Flashback
Apple removed the previous statement "It doesn't get PC viruses" and replaced it with "It's built to be safe," and "Safeguard your data. By doing nothing" with "Safety. Built in." [...]
In addition to changing its marketing messages, Apple has released a security guide for the iPhone operating system iOS and announced in February that OS X 10.8, or Mountain Lion, would include a new feature called Gatekeeper that would restrict which applications users can install on their devices.
Beyond the increased security features such as Gatekeeper making their way into OS X Mountain Lion, Apple is also working to reduce vulnerabilities in third-party platforms such as Java that are frequently exploited by malware authors. Apple has been working to shift responsibility for Java updates to the OpenJDK in order to make them more timely and has also been pushing out software updates to disable Java by default if it goes unused for a period of time.