The AF system has a function called Predictive Focus Tracking in AF-C mode. What this means is the camera will anticipate the movement of a subject and adjust accordingly - not just when 3D mode is selected. If you are holding down the AF-On button to focus, or the shutter release halfway with that setup, predictive focus is engaged and AF adjusts to subject movement. Predictive focus tracking has been around for a while and it gets better with each new AF system.
It may struggle with motion based on shutter speed, but if a subject is walking across a scene it will be tracked nicely.
I've found that predictive focus tracking works extremely well. I find it easier to manage using the AF-On button for focus since you can easily track a moving subject and fire multiple frames.