Turns out, yes. Yes, they are.
According to Wiki:
As detailed in "The Art of the Pirates of the Caribbean," the proposed story for the fourth film was for Sparrow and Barbossa to meet up in the newly founded New Orleans, before they sail to find the Fountain of Youth together. Johnny Depp signed on to return in September 2008, and Ted Elliott and Terry Rossio began writing under the guidance of producer Jerry Bruckheimer. The film is set for release in May 2011.
Geoffrey Rush has expressed interest in returning as Barbossa. Beforehand, Verbinski was hesitant about directing, and has now decided to leave this to direct Bioshock instead. Keira Knightley has stated that she does not wish to continue playing her character of Elizabeth Swann as she wants to do different projects.
In June 2009, Bruckheimer stated Disney would prefer the fourth installment of Pirates be released before The Lone Ranger film, which he, Depp, Elliott and Rossio had been working on for release in May 2011. He also hoped Verbinski would return to direct after his BioShock adaptation had been put on hold.
At San Diego Comic-Con 2009, Bruckheimer stated he intends to begin filming in April and May 2010. Rob Marshall entered negotiations to direct in August 2009. Hollywood announced a possible steam punk flare in the fourth installment.
On 9/11/09, at the D23 convention, the title was announced as "Pirates of the Caribbean: On Stranger Tides" with Johnny Depp in full Jack Sparrow make-up.
...Did you see that blurb in the last paragraph?
possible steam punk flare in the fourth installment
Steam punk pirates?!? WTF?
Anyway, they really need to leave this franchise alone. Yeah, Johnny Depp rocks as Jack Sparrow, but come on. It's like making another Star Wars when they KNOW it sucks. Oh wait... ;)