But the parks are going to be packed no matter what, Potter diehards or not. If you open in the middle of the insane crowds at an unexpected time, then at least there's nobody just blocking paths for an unopened land, and capacity will be swelled already. It'll run Potter thru the ringer with the normal theme park audience. Of course some diehards will worm thru, but around the holidays most are either on vacation already or concerned with their families. Social media or not, it's a strange time of the year where that sort of thing gets tossed out the window. It's such a perfect idea to catch them off-guard, in a time where you literally have to be INSANE to go to the park. (especially since you aren't guaranteed entry)
And, yes, some will try, fail or not USH will get that money. Happily, I may add. But it prevents the overswelling that might happen in the early winter months as a result of keeping the land closed.