The NFL and football in general isn't going to struggle anytime soon. They'll just gradually legislative more of the brute force out of the game. I think that while "purists" still like the aspect of the ground and pound side of the game, it will eventually evolve to something more along the lines of arena football in offensive theory, with simple stopping / slowing progress (without even tackling) bringing the play to an end. And as silly as that sounds, I think we're decades away from that foolishness. But it will still play well with the majority of fans now, who already think the entire game is summarized by the TD pass highlights they see on SportsCenter.
Personally, I think there HAS to be a better way to protect the head in terms of helmet technology. I'd be very interested to see the results of some "crash test dummy" style study where they use shells that aren't rock-solid, but actually give a little and absorb more of the impacts. But another part of me says that if it was possible, it would already be in use...
Maybe I'll build a prototype of my styrofoam / memory foam hybrid idea and pitch it on Shark Tank...