Ender's Game, as a short story, ended with Ender blowing up the alien homeworld, realizing he'd committed genocide, staring blankly into the distance, and then the two military guys are at a playground saying "huh. Kids!" The end. There really wasn't anywhere to go with it. That weird-ass 4th act Card tagged on to the novel exists pretty much so that he could dig himself out of a definitively done story.
A storyteller that didn't see himself as the messiah reborn would have finished with Ender in Book 1 and then followed a different POV.