If corals are going to die in their original areas, and might not colonize new areas fast enough, it might be an interesting endeavour for humans to attempt to colonize a suitable area. Take some native frags from aquaria out to a more northernly location than they were originally from. Attempt to match parameters as best as possible, and see if they take off.
Such an attempt would obvious have to be strictly monitored as to minimize damage to the new area, corals, etc., but it seems preferable to losing the corals entirely. Of course, I don't think we are quite at that point yet, but just a thought.
Cheers!