At Trilogy's End?

I keep hearing that "Pirates of the Caribbean: At World's End" is the final installment in the Pirates trilogy; however, after seeing the movie, it's quite clear that much is left open for a possible next installment.

I didn't see "Brokeback Mountain" so I can't say "Pirates of the Caribbean: At World's End" is THE worst movie ever made; however, it is one of the top two worst movies ever made.