Until all sub systems (ATC, dispatch, the plane, etc.) adopt AI driven collaborative decision making processes, capable of simulating holistic and naturalistic human decision making paradigms, it will not happen on a widespread scale. Sure a plane can fly from A to B undisturbed in a very controlled experiment environment. But without AI, and this is only my opinion, it's all moot. Think about your last flight and imagine synthesizing and somehow coding all the decisions that were made (Below/Above wing, dispatch, your crew, etc).

And then you have to ICAO regulate this to the lowest denominator (I am looking at you Kinshasa and Yangon FIRs). It'll be a while. It may happen, but it'll be a while.