the G5/Mid-Majors need the P5s more than the P5s need them. So to answer your question, I would say the DI schools (aka the NCAA) would agree to start a "pro league" within the NCAA before allowing the P5s to leave the current establishment. You have to keep in mind that the schools would still be subject to the current federal laws (i.e. Title IX) so even the P5s will be willing to compromise on what the "pro league" may look like to help control cost.

I am no lawyer and I didn't stay at a Holiday Inn Express last night, but I do think FSU's decision to privatize its athletic department could end up being a bigger move than what people realize. By privatizing the athletic department, the athletic department has essentially become an independent athletic organization which may not be any different than a pro team, country club, or private athletic club. If the athletic department takes it 1 step further and no longer receives any federal funding (directly or indirectly), then it may no longer be subject to Title IX or any other similar federal laws assuming the athletes are reclassified from "student-athletes" to "employees." At least I don't see how the athletic departments would still be subject to Title IX because they can easily argue they are now no different than the NBA, NFL, NHL, MLS, MLB, or any other pro/semi-pro league out there.