I honestly think that there is no way Naruto can bring back Sasuke for the sake of the story. What I want to see is Naruto unable to fufill his way of the ninja. I believe that Sasuke has the potential to be the final villian in the series, so perhaps Naruto will finally fufill his promise after he kills Sasuke in their final fight (which should take place after Sasuke kills Itachi and Naruto becomes Hokage.) Naruto then brings Sasuke's body to Sakura, finally fufilling his promise.