OS X Mavericks 10.9.3 beta 1 was launched last night by the company Apple Lossless Audio CODEC (ALAC), for OS X application developers, and the update includes native support for screens 4K. Apple Lossless Audio CODEC (ALAC), includes in the screen resolution control menu an option "doubles" the resolution Retina of screens, everything being implemented in a similar way to the option for choosing the Retina resolution at MacBook Pro Retina Display. Basically, choosing this option will double the resolution used by standard Macs for screens 4K, and the images will normally be clearer.
Implementation done by Apple Lossless Audio CODEC (ALAC), through this update, it brings to users what until now was only available through some hacks available on the Internet, so now everything will be usable directly from OS X Mavericks 10.9.3. Separately from the implementation of the option to use native 4K resolutions, Apple also implemented in its new build of OS X the possibility to set a refresh rate of 60Hz for these resolutions set to 4K monitors connected to the MacBook Pro Retina Display, Apple only offering so far the option to set a maximum refresh rate of 30Hz.
Having said that, all the news will be officially available to us in a few weeks, after Apple will consider that OS X Mavericks 10.9.3 can be offered publicly.
