Irrespective of his "silver" medal in the olympics, he is simply not silver medal material. It was one of the slowest all time 10k olympic final in a year in lacking the best talent.
Don't get me wrong, Rupp is a great talent. He is right up there with the best current US distance runners, if not the best. But he is simply not World Championship/ Olympic medal material.
He won't ever duplicate his accomplishments. Eventually he will make his mark in the marathon but that will be more like Hall's record - great showing, no wins to show for it.