I remember the NFL/AFL days. That wasn't good for football, and the merger took care of that. The AFC was formed around the AFL teams mostly. Lots of folks here don't recall that mess. The Bills were in the middle of it. They lost Pete Gogolak (kicker) to the Giants which started the bidding war. The bills went after Mike Ditka, the all pro TE from the Bears, then. It was brutal and teams and money was big for those poached. (not by todays standards, though) I don't have any desire to see another big time league form. But, with all the money out there chasing football, I would not rule it out. Maybe the Saudi's will bankroll a new league, ala the golf situation. That would be interesting to watch. Of course, you could argue that College football has become the alternate pro league.
As for Sanders, the young man has a tough road, who knows how it will play out. But, if he can play, he can succeed. (see Kurt Warner)