PEL MEL -- If Mel Karmazin was going to cut-and-run, he couldn't have picked a better time as far as Viacom is concerned. The company has two extremely capable successors - MTV Networks' Tom Freston and CBS' Leslie Moonves - though their co-president/COO status sets the Viacom-ers up for a bloody duel to succeed Sumner Redstone when he retires in the next three years.