One of the top priorities for the next president of ABC News won't be figuring out who should eventually succeed Diane Sawyer as anchor of the network's "World News Tonight." It will be deciding whether there will be an audience worth pursuing for "World News Tonight" when Sawyer walks away. With ratings and revenues declining and their core audience growing old, the news divisions of the broadcast networks -- like the newspaper and radio industries -- are struggling to reinvent themselves for the digital age. The playing field between traditional media and new media has been leveled, but the aftershocks are still being felt.