Being something entirely new, there is not a lot of direct experience on which to base a prediction. I’ve been at DL on the first day of the “usual” Halloween overlay at SM and HM, and the crowds were definitely higher than “usual” for that time of year. ANY brand new attraction is going to draw a lot of people on opening day; and the Launch Bay and SW overlay of SM are both new attractions. And SW has a HUGE (and somewhat fanatical) fan base. My “guess” is that TL will be packed beyond belief, and the other lands will have to absorb some of the overflow. There will probably be people queuing up to get into the park the day before and camping out overnight, so the crowd at the turnstiles at park opening will be very big. Personally, I would use “opening day” to go to DCA; the crowds in TL will probably be pretty big for weeks after the opening, but the “have to be their the first day” crowd will have come and gone.