From what we've learned today, I believe the queue is a series of interactive holding rooms and preshows. I suspect that while in a holding room you are able to explore and even remain in the room when the doors open into the next preshow area. I suspect that crowd control will be based on having enough people in each holding room that when the doors open into a preshow "theater" that enough people will enter moving the queue along. I don't think we will be allowed to remain in preshow theater spaces.
Basically, the holding rooms will be larger than the following preshow theater. I suspect that the greenhouse was added early in the queue process to regulate just this phenomenon. If you are finished in a room and wish to move forward, you just wait by the doors for the next show. If you are unable to fit into the next show, than you will most certainly be able to move much closer to the doors and make the next showing. I also believe that the final queue area, The Room of Requirement, will have an ample area of switchbacks to accommodate the ebb and flow of this type of line system.
On another note...
I suspect that some of you who have been following this forum have realized that StephenLandsman and I are old friends. I type this because years ago - hundreds (I think it was 1986) - Stephen and I traveled to Disneyland on an adventure we took together. When we planned our vacation, we were very disappointed that the timing would put us at the park a few weeks before the announced and schedule opening of their new attraction, Captain EO. There was nothing we could do to change our dates.
Anyway, much to our surprise we were very excited to find out that the announced opening was actually when it would air on TV, but the actual event was happening a few weeks early and while we were there. We had a choice, we could explore the parts of the park not effected by the celebrity festivities and enjoy shorter lines, or we could commit to sitting on Main Street or the hub near Tomorrowland and watch the red carpet arrival of the stars. As Stephen and I were avid Disney fans and had been to the park many times, we chose to commit to sitting for hours during the star-studded filming.
In addition, Tomorrowland was closed to the stars who after the parade were led into a roped off Tomorrowland, fed and given the opportunity to ride Space Mountain and of course, the first performances of Captain EO. Rumor had it that although Tomorrowland was closed off to the general public, that after the stars rode Captain EO, that they might open it up to the general public for the final few hours of the evening. There was no guarantee and standing by the ropes meant that we wouldn't be taking in any of the rides, but could get a glimpse at the stars as they passed by on their way to queue for Captain EO.
Again, we chose to wait and pray that we would "ride". It was actually a really cool time. A lot of the stars did walk by and some of them even came up to talk with us: Elliot Gould was a total gentleman and very kind; Molly Ringwald was an obnoxious, full-of-herself snob. There were many many celebrities and it was fun watching them.
Of course, we were tense and hopeful that they would let down the dividing rope and open the area to the public when the stars cleared out.
They did. Stephen and I were among the first audience who experienced, Captain EO.
One other quick note about this story... When we entered the theater, they had a camera set up facing the audience. Before they turned off the lights and started the film, the director of the upcoming commercial came out and explained that we were going to be extras in the commercial. He gave us a few directions and explained that at key moments en masse we would be asked to quickly lean left, then right, forward and back. We shot this sequence, they removed the camera and we got to see Captain EO. It was well worth the wait.
A few weeks later, when we were back home, they aired the Captain EO Grand Opening - parade and all. They also showed the commercial during the breaks and sure enough, there we were. Stephen and I still talk about this to this very day.
Stephen? Any comments?