I think the idea of having GSM link onboard is highly underestimated in commercial drone industry for the moment. Most drones we see on the market now has either rc remote controller link or WiFi link which both has FPV option but both requires direct visibility or very limited in range. Alternative could be GPS waypoints, that gives you an option to program your mission beforehand on earth and as soon as you run it you off the control of your drone. Even more you can do by adding just a little device that will track your drone in flight sending you GPS coordinates and point on the map where your drone is via GSM network. There are few devices on the market that can update waypoints on the fly. But real power of GSM and specifically of 3G/4G is that you can get both FPV and control over the same GSM link. That means you are limited just by your battery and GSM network provider coverage. Even more,  by merging these two technics drones will be able to fly by preplanned waypoints and at the same time pilot can watch live video from onboard and take manual control at any time if needed.

A lot of work was done over last 3 weeks. Finally moved server part from shared hosting to my own VPS. And finally moved away from apache/php SSE (Server Sent Events - data channel from server to browser) and Ajax (data channel from browser to server) to more lightweight and fast Node.js and web sockets technology (double way server-browser text and binary communication over TCP). Now there is no need to base64 encode JPEG data that was previously streamed over SSE as SSE allows only text data to be sent. Now both JPEG binary and control/telemetry text data is transmitted over single web socket. That gives at least 30% less bandwidth requirement for server-browser link and considerably reduces control latency.

Today is -20 °C freezing cold, but windless and sunny weather, so why not to try another distant flight, this time ~ 3km long.

Same setup: quadcopter, Naza M V2, 3G/4G GSM FPV receiver, Megafon 4G GSM modem, iPad.
Receiver is configured to run at about 60% of Naza pitch/roll stick range, which already gives about 30 km/h flight speed. So there is a room for improvement here.

Below is video from GoPro.