I think they will continue to open the park 15 minutes or so before official opening time for the foreseeable future. The crowds for Pandora will not die down for the summer and way beyond that. I think it is partially crowd management. There are not as many tapstiles at AK (or as much open space in front of them) as at the Magic Kingdom. Even prior to the opening of Pandora, AK would often open prior to the official posted time (as does Epcot and HS - however, at those 2 parks the crowds disperse to different areas as opposed to almost everyone going towards Pandora at AK).
I think that you would be at a decided disadvantage with a PPO Tusker House ADR if you want to do Pandora standby first thing in the morning. I think in order to be on the same playing field as those entering the front of the park (without the backway entrance being open) you would need to be out of Tusker House by 8:40 to allow for the walk back to the 'bridge'. That is a very quick breakfast.
That being said, it can't hurt to make the ADR and monitor the opening process in the coming months.
In my experience a couple of weeks ago, even during morning EMH 7:00 am opening, the tapstiles were opened at 6:40, rope dropped at 6:45.