I have a cousin who is an aeronautical engineer with drone experience.  He told me last summer that the tech to get an autonomous fixed wing drone is way easy and exists now.  Way cheaper to operate than multirotor.

Deconfliction technology to stay out of airspace of other drones exists now and is easy.  So swarms are easy, tech wise. 

Avoiding hitting stuff that doesn't move isn't very hard, he says. The things you can do without a human in the loop are wild, no G forces to worry about, etc.  Really frees up the designer to do things well within tech limits that a human can't physically do.

I gather that FAA/security is a huge issue, and FAA/registration/safety is a huge issue, and simply getting people used to that is a huge issue.  I don't see it happening any time soon here simply because of political issues/need for a long safety record.