I suspected something like this.

The subtitle to the next "Pirates of the Caribbean" is "On Stranger Tides," which happens to be the title of one of Tim Powers fantasy meets history novels, aka "On Stranger Tides."

According to Wiki, the Disney movie draws its "inspiration" from the Powers' novel...which probably means that the only thing that remains the same is the subtitle of the movie.

Here is a Johnny Depp fansite that has an interview with Tim Powers, who does not seem to know how Disney will use his book.

Still, it seems like Powers might be a good novelist to mine for movie adaptations.