The first beta version of the next update for OS X 10.9 systems has been released by Apple for Developer testing. The new beta can be downloaded now by registered members of the Apple Developer Program, either through the Mac App Store or through the Developer portal. There is limited information available on what bug fixes are included with the update, but Apple is asking Developers to focus on testing for Graphics Drivers and Audio.
Interestingly, the new update includes enhanced support for compatible 4K displays (discovered by 9to5Mac). When connecting a device running 10.9.3 to an external 4K display, Apple has included a Retina Display scaling option with output at 60Hz, which could mean that the company is preparing to update it’s own Thunderbolt Display with significantly greater resolution. There has been no word on whether this is actually the case, but since the last update to the Thunderbolt Display was over two years ago, it’s likely that an updated version will be released soon.