Pirates 4 is pretty much guaranteed to reach the billion and do a bit more. It's already one of the biggest grossing movie overseas. I think it'll pass RotK next week, so it'll be the third highest grossing movie overseas behind Titanic and Avatar (which won't get beaten anytime soon).
Comic book movies do okay overseas but not nearly as good as other blockbusters. See The Dark Knight, domestic gross was higher than worldwide. I don't see Green Lantern doing too good overseas, the franchise is completely unknown and it doesn't have the mythology aspect of Thor.
KFP2 will never reach its predecessor domestically (worldwide is up in the air as there are still a handful major territories where it'll do big), that's pretty sad