Well, there are plenty of football fans (and sports fans, in general) that will pay $$$ to watch a single game, and many more that like watching it on TV enough to schedule their lives around when the football game will be shown. Myself, I'll watch a game every now and then, and I have a general idea of how well the teams that other people in my family root for are doing.
As for whether fans would follow their games onto cable, in the cases that they don't already have cable or satellite, I'm sure that's a question of statistics. Some percentage will follow the sport to cable, some percentage will do more illegal online streaming, some percentage will just google the score after the game, some percentage will just stop watching. "Football fans" are different people, so they'll react differently.