The 2013 Mac Pro isn't the only member of the 4K Klub — 2013 MacBook Pro Retinas can too
You Mac pros don't need to wait for your Mac Pros to try 4K. The MacBook Pros can too, if you have one of the 2013 Retina models.
Here's Apple's KB article on the subject:
The following Mac computers are capable of viewing 4K resolution via HDMI from Final Cut Pro X 10.1.
- Mac Pro (Late 2013)
- MacBook Pro (Retina, 15-inch, Late 2013)
- MacBook Pro (Retina, 13-inch, Late 2013)
The supported 4K resolutions are as follows. Note that not every 4K monitor will support both of these resolutions, and 4096 x 2160 is only supported via HDMI at 24fps.
- 4096 x 2160
- 3840 x 2160