How is the OMD so fast

I don't see why CDAF systems can't do tracking as well in the future for stills.  PDAF has an advantage in that it is predictive, but with frame rates of 10fps you just need to get focus right every 100ms.  a CDAF based system would seem to need to 'wobble' to check focus, but if everything else was fast enough it could keep up with a moving subject.  it could also bring with it the advantage of tracking by color anywhere on the sensor.

I would say that adding PDAF to the sensor seems logical since it seems technically easy enough to do, but the only downside of a fast CDAF tracking system is the user experience seeing it go in and out of focus slightly - but that doesn't mean it can't ever keep up with fast moving subjects...  A really clever system in the future with faster chip readout could even hide the wobble by skipping a few frames in the EVF

CDAF has accuracy on its side - and works in both the viewfinder and on the rear screen without a pellicle mirror that adds distance to the lens mount.  It will keep getting better.  There is a big difference between saying PDAF is better NOW, versus saying it will always be better.