Apple appears to be adding 4K support to Mavericks, according to a recent report. In the latest beta version of Apple's OS, there is reportedly an option available to run the system in native 4K for use on Ultra HD displays. Based on the hands on report, Apple is calling the native 4K feature "Retina" inside the Mavericks ecosystem.
Many expected Apple to add in full 4K support to OS X, as the technology is becoming more and more accepted. While there are no official confirmations at this point, the user was able to run Mavericks beta 10.9.3 in what appeared to be native 4K on a Seiki Ultra HD display.
Macs already support 4K but it is not a true representation of the resolution, the OS simply resizes various elements in order to properly scale up the operating system's UI. With the new pixel-doubled 4K resolution support, images look much sharper and clearer than with the current option, according to the report.
Another detail from beta 10.9.3 that surfaced appears to show late-2013 Retina MacBook Pros with the ability to drive 4K displays at 60Hz. Apple currently states that the rMBP is only able to push a 24 or 30Hz 4K display over HDMI. While Apple's new Mac Pro already supports 4K at 60Hz, this feature would essentially streamline the process.
The report also suggests Apple could have its own 4K display in the works now that it would appear the software end of the system is being taken care of. This could lead to hi res iMacs down the line, but more likely 4K Apple cinema-style displays.