I think it's a bad assumption to think the NFL will demand more money when ratings and subscriptions are down. ESPN just has to be the highest bidder. Someone has got to air the games.
What happens if the highest bidder can't pay the NFL enough to make it worthwhile? I keep seeing pictures of half-empty stands behind kneeling football players, and ultimately if the NFL destroys its value by alienating too many fans with politics, there's no reason the entire business won't or shouldn't collapse.
Think about it: an NFL team sponsored by the alt right vs. one funded by Ben&Jerry's.