You are right, with the current state oft LTE and a digital video pipeline we are not yet competitive to analog latency. On our Sky Drone FPV system we get a glass-to-glass latency of ~150ms which is good enough for controlling a drone at some altitude. It is not good enough for competitive racing though.
But I am confident the time will come. The next gen cellular network aka "5G" will reduce the network latency significantly and with some new technologies on image sensors (super high framerate, global shutter, ...), I am confident that it will eventually make analog setups obsolete.
Unfortunately DJI is not very open to third-party integration (at least for their consumer drones). So while you will get unlimited range with our LTE based Sky Drone FPV system, controlling a DJI Phantom is not possible. Any other drone with open serial telemetry port will work though - like all the PX4/APM based drones.
We are looking into low-latency Dual-Full HD video streaming for the next Sky Drone FPV solution with real 3D Oculus Rift support :) 300Mbps would come handy
Real END-TO-END LATENCY shots published for Sky Drone FPV project, showing 170ms and 184ms end-to-end latency with the prototype setup. We will make sure to end up at <150ms at launch!