"We're going to shoot Pirates 4 in April and May of next year. We are going to release it hopefully in 2011. Pirates 4 would hopefully be the first of another trilogy."
Walt Disney's Head of Production Oren Aviv
Also thanks to Hollywood Elsewhere, via one of their trustworthy sources, we got confirmation of the Fountain of Youth plot with Captain Jack Sparrow (Johnny Depp) looking for the legendary fountain. And it seems that a new villain who's a kind of Captain Nemo utilizing new-style technology will be introduced.
It's not yet clear though if Director Gore Verbinski is returning: Disney wants to scale down the movie budget, so it's not sure Verbinski would come back..
Well I really hope they start filming asap so we may watch the movie Pirates of the Caribbean 4 in 2011.