Burton had been looked at for Pirates 4 but never signed on. He's becoming a studio stable with Alice In Wonderland, Nightmare Before Christmas, Frankenweenie and his Sleeping Beauty project Maleficent. I like the idea of Burton entering the world of Pirates but I'm not sure he would deliver a film any better than the previous ones.
Sam Raimi is directing the studio's next big fairy tale picture Oz, The Great & Powerful the Oz prequel which focuses on a young wizard. Raimi seems like the safest choice out of the bunch and could give audiences a fun film if given breathing room. My only concern is that he also had been working on pre-production for Warcraft which is likely his next film.
Alfonso Cuarón is the director that should be turning heads. His wonderful film Children of Men proved he's got the visual and storytelling chops that most directors inspired to have. Giving audiences family friendly entertainment with The Prisoner of Azkaban while keeping his dark style. Alfonso also has the promise of pumping the new blood needed to keep the franchise going. Unlike Raimi and Burton, Cuarón isn't deep in development on other large projects.
The filler choices seem to be Shawn Levy (Date Night, Real Steel) and Chris Weitz (Golden Compass) neither directors of garnered praise or success for their previous films as of yet. Levy is set to direct a remake of The Fantastic Voyage for producer James Cameron. There have also been talk of other projects with Hugh Jackman including a Real Steel sequel. Weitz seems an odd choice and left field when compared to the other candidates.