3. Peter The Hegemon
Peter becomes the Hegemon of Earth after the Buggers are defeated. Using his influence as Locke, he brings an end to the League War, and is forever remembered for being a caring and peaceful leader (his actual ascension to power is explained in more detail in the novel "Shadow of the Hegemon"). The irony here is that Peter is remembered as a hero, despite being cruel and violent as a child, and Ender is remembered as a warmonger and xenocide, despite being the more kind and gentle soul.
Why We Probably Won't See It In The Movie: Seeing Peter ascend the the role of Hegemon will feel completely out of place if we don't see
how he gets there, and if we aren't going to be seeing the subplot involving Locke and Demosthenes, we probably won't be seeing Peter's destiny. Perhaps we'll see hints of it, but any mention of a 12 year old becoming leader of the world will feel completely ridiculous, no matter how much audiences are willing to suspend their disbelief.