Dont know if this helps or not, but from previous experience elsewhere with "Grand Openings" of attractions or areas, usually only a limited amount of folks (VIPs, contest winners, invited guests, press, etc) and a limited number of regular day guests are allowed in the general area until after the Grand Opening ceremonies are completed. After that and some clean-up, the area opens to everyone just like any other normal day.
Have to remember that during these ceremonies there will be stages set up, cameras set up, areas for VIPs, press, etc. And little or no motion going on (rides not operating or at least not admitting guests, shops will be closed, etc).
There are also other things to consider like fire codes, crowd control, safety of VIPs, and so forth.
So, if you are going on opening day, try but dont EXPECT that just because your in the park you will be admitted to the ceremonies without a special pass or ticket, and with a 9am park open, I would not expect regular operations in an area like WWoHP and its limited access points to happen until at least 2-3 hours AFTER the ceremonies are concluded, if at all that day because of all the extra equipment, stages, etc that will most likely be erected.