I am basing my theory on the title alone. At Twilight the Moon comes up. in the book Edward comes into Bella's life. so Edward = Moon. When there is a new moon there is no moon in the sky at night. In the book Edward leaves meaning no moon. An Eclipse is when the Moon blocks out the sun. in the book Edward is back and he blocks out Jacob. At Dawn the Moon goes down and the sun comes up. So in the book Either Bella chooses to be with Jacob, Edward somehow becomes human, or Bella becomes a creature of the night. I hope it's the later of the three. the only way that SM will be able to make everyone happy is if Jacob imprints on Someone Else, or if Bella gets hurt and the only way to save her is to make her a vamp, so then Jake is all for it. Take your pick. But I just plan on being upset by the outcome so that I'm not depressed if it doesn't end the way I want it.