Disney already has a full slate in summer 2015 with Avengers 2, Star Wars 7, And Man and a Pixar animated film.
Other studios bring the likes of Batman & Superman, Terminator and Jurassic Park films into the mix. Even good films can get squeezed when there's just too much competition for the public's dollars. Mediocre films get annihilated.
I don't know what this says about relations with Bruckheimer / Depp, but switching POTC to another year when Disney doesn't have it's two top franchises in play (Star Wars, Avengers) sounds wise to me.
I can't see Disney giving up on POTC unless they are unable to meet Depp's payday. But he isn't exactly at the top of his game right now. Disney isn't the only studio reluctant to pay Depp the dollars he was earning 5 years ago.