I could easily seem them doing away with EMH, replacing that perk with something else (like a 4th Fast Pass) and then offering special nights that the park is open late at a special guest.
Like a party, but cheaper (and less overhead since they won't need to do anything special).
I just wonder how many people would be interested in paying $X for going to the parks late at night. (especially when they've been offering it for free for so long).