IT ALL ENDS JULY 15

Seldom has a marketing slogan offered such direct insight into the Hollywood psyche. July 15 was, of course, the day Harry Potter and the Deathly Hallows, Part 2 opened, concluding a decade of Potter movies with, as it turned out, an enormous bang — $481 million in weekend ticket sales worldwide, eclipsing all box-office records and leaving studio executives gasping for adjectives.

Clearly the slogan worked.

But the end of a $7 billion movie franchise for Warner Bros. was hardly the end for fans. In fact, you could just as well say “It all begins July 31.” That’s the day fans ...