Do you honestly think the viewership #'s won't be flipped in AMZN's favor by 2021? ESPN may be dead in 10 years and I would not be surprised to see them spun out of Disney and run by private equity firms within 5 years.
The NFL will ALWAYS find how, when and on what devices people watch the sport. The NFL billionaires will always make their money. The question is how much they will want to play with Roku, AAPL, GOOG, AMZN, etc. in the future. Content distro deals are going to look a lot different.