Apple has just seeded and released OS X Mavericks Gold Master (GM) to developers for testing. The GM release indicates that a Mavericks launch is near, and this build will most likely be what is released to the public (bearing any major bugs). We expect to see an OS X Mavericks public retail release sometime in the last two weeks of October.
Earlier today, this build was seeded to select AppleSeed members.
Also released to developers is: Xcode 5.0.1 GM seed, OS X Server Preview 9, and Apple Remote Desktop 3.7.
The new updates can be grabbed via the Mac App Store or here.