I could some combo of Apple, Facebook, Google-YouTube, Amazon, Netflix, even Twitter, soon outbidding and wanting to replace the traditional CBS, Fox, ABC-ESPN, NBC. We now can watch many games on Yahoo - which is no tech titan.
I think it harder to quantity tv viewership over online viewership which is data driven, unless cable tv providers and satellite tv are providing this data.
With 5G coming online I can see how by the end of this decade a majority of NFL games will be watched over cellular networks.