I'm sure the creative teams would love to develop completely new experiences each year, but... with what money? They need a return on investment for the stuff they already paid for. I suspect this event will evolve similarly to the earliest years of the Horror Nights relaunch, where we see a fair amount of repeats along with a new marquee experience or two per year and differing street entertainment (to your point, more characters and mini shows). I could see Waterworld happening next year, though, especially now that they have so much evidence that One Piece does gangbusters.