Sean Hannity may not be worried about the 2020 election — if he is, he hasn’t said it on his Fox News Channel show — but his ultimate boss has indicated media investors might have some cause for concern. The executive who has final oversight of Fox News Channel suggested Tuesday that the surge in audiences enjoyed by news networks may fall noticeably after the 2020 election — a development that could have ramifications for some of the nation’s biggest media companies. “I would expect that as we enter a more normal news cycle, which will happen eventually, that appetite...