Football will never lose a fan base. If anything, we will become more rabid. Im not a pro fan. I prefer college. But diehards will not allow this sport to go to hell. A great portion of america lives for football. Their lives are based on travelling, tailgating, and attending games.
At one time, boxing was the most popular sport in America. That changed. As Gregg easterbrook likes to say, there is no rule that the NFL has to be popular.
This is a serious issue for football. It has to figure out a way to eliminate concussions or it will be marginalized as a sport.