My daughter spotted (or thinks so) that this is the last of the Chronicles to be adapted, since the snippets of the end in the trailer seem to show Peter and Susan at the waterfall at the End of the World; suggesting that they will either end it there, as per The Last Battle and its explanation, or the children will return to their lives, and live them out without any reference to train crashes or Susan's falling away from believing in Narnia and what it stands for as primary in her life.