I would say no it will not be open. It is closed now in the middle of the Summer. We were there last week and even went inside it during our EPCOT Future World Tour. The Guest Relations cast member said it was only planned to be open during Christmas Season and possibly during special events at the park. September is one of the slowest months so I can't imagine they would have it open then.
He stated it was just not as popular any more, it was a fairly high labor intensive pavilion to run and that with Soarin, Test Track and Space open it was not seeing enough visitors so they closed it.
The funny thing is when you walk in the lights are on, the air is on and everything looks like it's 'running'. They do that he said to preserve the condition of the pavilion and not have mold/mildew take over.