I guess you don't follow the sport but you can easily see Bob Kennedy, Ritz, Webb, Goucher, Carl Lewis, Leroy Burrell, you name it.. Some people completely let it go and pack on weight, others keep fit and trim.
My experience is that most really elite distance runners do something else. Those that have really achieved tend to move on, while those of us that were mid packers in college slog on doing road races, marathons, etc. (Maybe it's a case of arrested development, maybe we just really like running, probably a little of both.)