updated 04:34 pm EDT, Wed August 7, 2013
Mavericks changes yet to be discovered
Apple is seeding updated betas of OS X Mavericks and the next version of Mountain Lion, 10.8.5. Mavericks has reached Developer Preview 5, which registered developers can download via the Mac App Store. Any further additions to the OS have yet to be documented; the completed version of the software should ship sometime this fall.
OS X 10.8.5 is now in its eighth beta, continuing a weekly update cycle. Bundled as part of the code is Safari 6.1 beta 5, but otherwise no critical changes have been announced. The v10.8.5 update will likely be the last major release of Mountain Lion.