Here is the Disney banner for POTC4 and 2 pics from the D23 expo with Johnny Depp appearing onstage in full Captain Jack costume with Disney Chairman Richard (who goes by a common nickname that this site filter doesn't like). Cook. *Banner and photo credits to Karen and Mim!E from JohnnyDeppReads.com, respectively:
You can go to Amazon.com and read a user review of the 1987 book On Stranger Tides by Tim Powers. The story, boiled down, is about an English puppeteer-turned-accountant who is press-ganged into piracy. He encounters actual historical figures and places including the governor of the Carolina territories, Juan Ponce de Leon, Blackbeard the pirate, and yes, the Fountain of Youth.
No word yet on if the POTC4 script will follow the book at all, or is just borrowing the title or what.