Apple just sent out an email to developers, notifying them that three new downloads are now available: OS X Server Preview 7 for OS X Mavericks, OS X Mountain Lion 10.8.5, and Windows Migration Assistant.
OS X Server Preview 7 for the upcoming Mavericks operating system is build 13S357e, which focuses on Wi-Fi, graphics, wake from sleep, PDF viewing and accessibility, and mobile device management.
The latest seed for Mountain Lion, pre-release build 12F36, has the same focus areas, and has a combo (all the files) or delta (just the new changes) updater.
The Windows Migration Manager is Version 22.214.171.124, and sill help Windows PC users migrate their data to a Mac running OS X.
Source: Apple Developer