So this article confirms that to one extent or other, PotC4 does look to be based on the Tim Powers book On Stranger Tides. Powers’ attitude? Much more realistic and healthy than my own, as I still cringe to see a single on of Powers’ characters usurped by Barbossa or Sparrow. But as some readers pointed out, you can’t judge a movie until you see the movie, which is true.
I still find Disney’s need to harvest pre-existing texts as a bad sign – it could well mean they’re looking for a short-cut fix to not having any story ideas of their own. OR, maybe they’ll spin gold out of it – I’ve certainly been wrong before.