I agree with MasoKnight, and this was something I was thinking even before the leak. Seriously, I really works putting it even before Mylo Xyloto.
Try it. Listen to Moving to Mars, and pay attention to the sounds right before it fades, after Chris has stoppped singing. I think these sounds could just continue for some seconds more and then blend into a burst of Mylo Xyloto. That would be awesome!
Also, if you listen to the lyrics, although they are kind of meant to be the "bad ending" of Mylo Xyloto, I think they would just as well fit as a prelude to everything, kind of like a prologue to a fiction book.