Media event set for September 9, launch likely ~10 days later.
Apple Releases OS X Mavericks Developer Preview 3
The third iteration of the OS X Mavericks beta comes two weeks after Apple seeded the second version to developers, focusing on performance enhancements and bug fixes.
OS X Mavericks is slated for release this fall and includes new features like a tabbed Finder, full screen dual monitor capabilities, Safari improvements, and a new Maps app. Developers can receive the update via the Software Update tool in the Mac App Store.