I think the concern is that this might eventually replace free EMH. For the preliminary offering they will probably schedule it for non-morning EMH days. But if it is successful how long before they eliminate free EMH in order to free up days for the paid event? I have a hard time believing it will be successful, but I'm sadly likely to be wrong.I would hazard a guess that this will not impact the park when they are offering regular EMH, simply because regular EMH gives you the run of the park, and this is a limited experience. It would be easier to implement on NON-EMH days where they can just not open the rest of the park.
I'm also surprised they are risking cannibalizing BOG breakfast by likely eliminating the pre-RD advantage on the days this event is offered. But maybe they've found BOG fills regardless (for example on 8 am open days when there is no advantage).