A question of the splitting factor for the two power houses. A friend from work mentioned a theory that the Phoenix was the issue that split the old friends and set them on thier paths. What if Professor X discovered that Jean was harboring the Phoenix force and his disicion was to contain it? This would grind Magneto the wrong way because of his stance on what mutants actually are. Also it would explain why the Phoenix comes after Professor X. In one of the previews Wolverine tells the Professor X that when you cage a beast long enough it will strike back. The rumor of Professor X's death would be explained.