I never thought I'd say this, but the playoff system sucks. Yes, maybe the playoff doesn't influence whether fans of Nevada watch the Famous Idaho Potato Bowl, but it definitely influences where the top recruits want to play.
53% of 5-star recruits get drafted. It's 20% for 4-stars and 6% for 3-stars. With just a glance at the Rivals 250 over the past few years, it's more than obvious that 'Bama is dominating the market for 5-stars and that an overwhelming majority are signing with one of the 8 programs that have made the playoffs at least twice since inception.
The result is that Alabama is bordering on an NFL team and there is wide disparity between OSU, Clemson, Georgia, Oklahoma, LSU, ND and everyone else. Texas, Texas A&M and Florida are the only programs with a fighting chance to break into that second tier. Everyone else is basically playing for the Famous Idaho Potato Bowl.
I also don't think expanding to 8 teams changes that much. Over a 10 year period, I'd expect 70 of the 80 playoff spots to come from the list of teams above.