I'm guessing that Kishimoto was so pissed at the way the fillers were going he just one day went "Jesus! It really isn't that hard, asshats!" and whipped up a script for a filler plot arc in around twenty second, and that is what they're going with now.

And I think it would be Pirate Ninjas, as they are Ninjas who have become pirates. Ninja Pirates suggests to me Pirates who have somehow received Nija training to aid them on the high seas. Avast! Shiver me shurikens!