For what it's worth, in the April 2013 issue of British movie magazine, TOTAL FILM
, they include a multi-page Summer blockbuster preview. In it, they finish each preview with a predicted global box office figure. STID is forecast to take $810m. Personally, I think that's probably just a tadge optimistic. For comparative purposes, they have Iron Man 3 set for $710, Fast 6 at $680 and The Lone Ranger bringing up the rear with $580.