Is your point, that in the future terrorism will be a sustainable ever growing force?
Since as long as violence is not tolerated, is brought toljustice in one way or an other, you are trying to kind of solve a nonexisting threat.
I mean yes someone is and will in the fututre kill with drones. But as long as the actor looses power, in my eyes all is fine. In the example of Putin we can see this clearly. He attacks and pays with all his power.
And like this is every act of violence. A threat actor can only hold power as long as he does actually use power rarely. A kidnapper, which just kills the kidnapped people, will not make no money.
So what is even the threat you describe? You really make very little effort to make me understand your ideas.