Just a guess, but I would imagine they are following attendance right now with multiple shows and crowds in AK due to Pandora.
Maybe waiting to decide the schedule during that time of year when they have more dark. At one point they had talked about three shows. With the new hours, can they fill three?, will two do? or at that point will interest have dwindled and maybe one show. Or even possibly, like Fantasmic did for awhile, shows only a couple days a week. And all this has to be coordinated with the Dining Package, so it's probably a math thing on making it work best.