I was lucky enough to attend a career fair presentation today by a project manager with WDI who works on Animal Kingdom, and he shared some Rivers of Life information.
He specifically said the theater was designed for 5,000 guests a show with the intention of 3 shows a night, with the intention of extending park hours to 11pm or later.
When he was talking about the physical elements of the show, he said that the lanterns on the water seen in the concept art are basically gps controlled mini boats that can be used to make patterns in the water, and that there would be approximately 150 of them in the show.
Also, he mentioned something about water screens and projections coming from moving boats, not just stationary barges. It seems to me that the shot of the bear running across the water in the youtube video could be one of these moving screens.
He seemed very excited about the show, as well as everything else happening to the park. His project is Avatar, so he mostly talked about that. All very cool.