Something a lot of people have overlooked is the performance aspect. Granted, it won't work for anything other than freighters, but no pilots = no real need for pressurisation unless you are carrying livestock. No bleed air demand = a what, instant 10% improvement in engine performance. Longer engine life, higher ceilings, or lower fuel flows for the same flight envelope. No pressurisation requirement = a lighter structure for a given strength, and/or no airframe cycles with their associated maintenance requirement.
It'll be a loooong time before we see it with passenger aircraft, but I would be genuinely surprised if I don't see autonomous freighters in my lifetime.