Since the NCAA is essentially a pawn to the P5 programs, expansion of the playoffs will never happen until they decide they want even more money.
And then it'll be rigged in their favor, because if this was based on what is good for the entire FBS membership, there shouldn't be just one slot reserved for a G5 program.

There are 130 FBS schools, P5 conferences include 70 (so not including independents), 70 constitutes 54 percent. If three spots in an 8-team field went to G5, that would still only be 37.5% instead of 46%.
THAT WILL NEVER HAPPEN, but the truly equitable formula would be to include TWO schools from the G5 ranks. That would mean 75% of the field would still belong to the P5 -- SEC, B1G, ACC, Big XII, and PAC12 -- champions plus the next best program.

So the best scenario is for an 8-team field and guaranteeing one G5 berth.
Do away with either the bye week or one non-conference game to allow for the one additional game that four schools -- out of 130 -- would have to play to get to the championship. And if the NCAA had any power, limit every P5 program to no more than seven home dates out of 11 games (conference and non-conference combined).

Of course REALITY is the same as taxes, the rich create the rules and loopholes to ensure they and only they get richer.