IMO, the question here becomes one of acceptance by the fan base. There are gay players in the NFL already. That's a given to me.
Lets say the door is opened. Lets also say that a team manages to have two or three players that come out. It would stand to reason, at least to me, that a gay community might want to support said team a bit more. Would that mean that all of a sudden, the traditional fan (we'll call them) would be sitting side by side with Gay fans at the local sports bars? If so, would they accept each other? The problem would be fans and how the NFL views there acceptance IMO.