A three-minute trailer of the second film will be added to the first film in America next month - but fans will have to sit through all three hours to see it!
That's because it's going to be added right at the very end of the film, just before the credits appear.
No one's sure if the copies of the films in British cinemas will do the same thing, but let's hope so!
He was speaking to an incredibly lucky group of fans at a bookshop in America.
He's in America at the moment because it's awards season - and all the big names are trying to get noticed by the people who vote for the Oscars.