I strongly believe that the NFL will cease to exist as a major sports league in the foreseeable future (< 25 years). It increasingly seems that CTE is an unavoidable side effect of the game, and as that reality really registers with parents the steady supply of young players is going to dry up. I've heard people say that it will end up a niche sport like boxing (which has its own obvious brain trauma problems), but you need a lot more potential football players to maintain a viable league than you do potential boxers to maintain the level of professional boxing we have today.

edit: typo