But those fans are already watching. The question to answer is whether a super-conference that excludes many schools in non-SEC or Big10 fan bases, would attract MORE people to watch than watch today or less? There are definitely people that they will lose. For example, a BYU alum that grew up in Utah and cheers to BYU both from school loyalty and regional loyalty. But who are the people that they will gain? Are there casual fans that don't watch the CFP today that would in a future world where they have even less potential association with College Football? I think that number is probably small.
It is probable that the 2 conferences could "take their ball and go home" and capture all the $'s associated with the CFP instead of share it with other schools/conferences. At least for a time. Americans, as a whole, tend to have a sense of equity and fairness that will play into this at some point. We love underdogs and hate bullys. I have a hunch that while the SEC/Big10 plan might produce a windfall for a time, at some point, people will start to tune it out. It will neither be the best football (that is the NFL), nor will it be all-inclusive (that would be a tournament like March Madness that gives everyone a shot).
My belief is that if they continue down this path they will find that they have killed the goose that laid the golden egg. Nice for a short bit, but short-sighted in the long run.