I'm not smart enough nor do I have a crystal ball that will determine when Coz will/should open. It's truly a rock and a hard place scenario between two diametrically opposed forces. Sort of reminds me of the movie "Jaws"...the scientists/oceanographers/marine biologists were saying 'stay out of the water', while the merchants and Chamber of Commerce were downplaying the shark threat cuz it was eating into the tourism business. (No pun intended).
I would, however, LOVE to be one of the first divers in the water once the marine park opens, just to see whether the lack of cruise ship traffic has improved the health of the reef.