I suspect that the introduction of “flying cars” (I hate that term but that’s what they’re being called) or use of bigger drones will cause a series of attacks on the general population in the likes we have never seen before. 9/11 being one of the most drastic examples, buy these being committed but otherwise regular citizens. Some suicidal half-wit wanting to cause harm to someone he hates as he kills himself, or some psychopath crashing a drone with explosives into a crowded area. This is already being used for attacks as was the case in Saudi Arabia oil refinery.
There will likely be two developments: anti-drone automated defense guns shooting nets or in other cases electromagnetic waves disrupting these from entering certain airspaces. This in turn cause problems of their own since accidents can happen, and some of these attacks will be using regular airways available to them thus these defenses only work for isolated areas with strick controlled airspaces.
What you’re likely to see develop is underground construction making these air attacks irrelevant.
In an ironic twist the mastery of the sky by anyone will lead to a descent underground. This descent underground already exists with the rich in places like London.
https://en.m.wikipedia.org/wiki/2018_Horizon_Air_Q400_incident
https://www.businessinsider.com/ap-police-man-flies-plane-into-his-home-after-fight-with-wife-2018-8