As already reported by many sites, Apple seeds OS X Mavericks 10.9.3 build 12D12 to Developers.
Details of this seed is covered by Apple Developer NDA, but it didn’t stop any of the sites (1, 2, 3, 4, …) from mentioning them.
In the mean time, Apple Developers are anxiously waiting for the GM or release build of iOS 7.1, since the current build (beta 5) has the goto fail vulnerability.
When asked about the release date of iOS 7.1, firstname@apple.com simply said “soon.”