I wish one could put that genie back in the bottle, but I fear that lion fish are here to stay. It only took a very small number of lion fish introduced to the wild to reproduce and spread all over the Caribean. Divers are not going to be able to track down every lion fish in the ocean and kill them. Even if a few were missed, they would just reproduce right back to their current levels. History shows that elimination of an introduced exotic is almost impossible.
Now, one hopes that the local predators: sharks, grouper and morays can learn to hunt and consume lion fish. Some predation could possibly keep their numbers in check, but I am not that hopeful.