The retirement of NBC Nightly News anchor Tom Brokaw may be the beginning of the end. Dan Rather claims his earlier than expected retirement from CBS Evening News had nothing to do with his Memogate scandal. But we all know better. Peter Jennings may be safe at ABC World News Tonight, for the time being, but the same can't be said for Nightline's Ted Koppel. Two years ago, ABC nearly dumped Koppel as it pursued David Letterman. Although ABC eventually backed off, Nightline's meager ratings and suspect credibility has indicated the end is near. Nightline's executive producer, Leroy Sievers, was...