I agree the chance of a drone bringing down an airliner is very small, not zero but very very small, The chance of a drone causing serious damage because the dense and heavy battery went through an engine or windshield is also low but very definitely not zero. If it does happen then there will be a shyte storm of epic proportions, yes still high consequence but low probability and it will mean some airplane got very unlucky.
The more interesting question is when will airports treat drones like birds. Airports don't shut down operations when somebody reports seeing a bird, so IMO the Gatwick fiasco was the tipping point. I think the airports must now be doing the risk reward calculation which is has got to tend toward continuing operations after a drone report with some sort of advisory caution given to pilots.
Personally I am more afraid of L asers than drones.