Obviously the whole point with duty-free is that it is entirely contingent on passage outside of national boundaries. You're simply not dealing with one nation's government, you're dealing with all of them.
Apart from ICAO, and their maritime opposite numbers having to liaise between themselves and every country that allows duty-free concessions, shutting it down entirely would put many thousands of people into the dole queue, and shut down valuable income channels for many companies.
Additionally, and most importantly, where else am I going to get a litre of Johnny Walker Blue Label at a decent price?
I see the point with regards to volatile liquids in the cabin, but there would be a mountain of public opinion, politicking, and paperwork to get through before it happened.
I'd hope it ends up in the "too hard" basket.
The next step would be to ban spirits on flights entirely (there are probably stronger arguments to do this than to ban duty-free), and that would take alot of the fun out of life.