I think it will be a "2 steps forward, one step back" path, like autos. The tech will reach a point where proof of concept looks stellar. Drones humming along, model of efficiancy. Then one plummets to earth in a fireball, killing multiple humans, and the fleet is grounded. Insurance companies demand a fullproof software fix since they're defending multi million dollar lawsuits, and the media attacks this new exotic death from above. Then slowly the public gets used to the occasional crash, and the tech gets amazing, and it becomes the norm. But that's over a 15 to 20 year span we're talking about.