Bryan Singer said in a interview today that he would like to return to helm another X-Men movie. Singer was the director for the first X-Men movie as well as its sequel X2 X-Men United both produced by Fox studios. Singer was not around however for X-Men 3 the Last Stand opting instead to tackle the Superman relaunch.'
Perhaps someone like Jon Favreau, who directed the Robert Downey Jr. movie Iron Man could take a crack at it. He seems to be able to find the right balance of action and story.