U.S.A.
Transformers 3, the previous one wasn't good but I don't know with Americans LOL. This one looks promising though
Worldwide-
Either...
Harry Potter Deathly Hallows Part 2 and it's super possible it'll break $1 billion barrier as it's the final film of the movie franchise and to be shown in 3D(Part 1 was shown in 2D only and according to BoxofficeMojo it was the most attended film of the 2010/most tickets sold only beaten by films such as Toy Story 3 and Alice In Wonderland due to higher prices on 3D tickets when it came down to Box office Gross)
or
Pirates of Carribean: On Stranger Tides- due to Johnny Depp hype as usual, but it may take a bit of a slide due to two of the main protagonists out of the film(Keira Knightley and Orlando Bloom) and it's possible that most people who watched POTC series thought it was a trilogy and At World's End was the last film of the series. LOL
And LOL at MI3. We're on MI4 now bro. Idk bout this, but eversince the Oprah couch incident, there's been a decline in Tom Cruise's Popularity.