When the Big 10 and SEC expanded and then NIL made it legal to pay players, it became inevitable that college football will eventually split into a top tier semi pro league that pays players and has their own playoff. Then there will be multiple lower levels that play bowl games, The Big 10 and SEC will operate like an AFC and NFC.
I expect that in the end the top tier will only have about 40 teams, maybe less. These will be the teams that can afford to pay players and compete. Mid-range teams like Michigan State, Pitt, Arkansas, etc, will eventually want to play at the lower level. They will get tired of being a farm team for the big money programs. They'll have a freshman phenom and then next year he'll play for a big money team. That will get old fast.
North Dakota State has tons of success at the FCS level. People have asked why the don't bump up the the FBS. I'm sure they could compete but would they win? Wouldn't you rather stay in the FCS and compete for championships instead of going to the FBS and marking the Weed Eater bowl as a successful season?
Maybe they will reserve 2 playoff spots for the lower level teams just to keep it interesting, but I can't see any soccer style relegation. College football doesn't work that way. A small school like Iowa State might have a great season and next year they might suck because they lose players to NFL and to transfers.