If the favorites play out as expected, I'm happy with the current final four grouping. I don't really see a 5 or 6 that I think merits inclusion.
The biggest remaining games:
Bammer: They still have Miss. St., Auburn, and the SEC championship game against Georgia (with a sandwich game against Citadel). Not an easy path, even if they lose once they are probably still in. If they lose to a 1 loss Georgia, they are probably both in.
Clemson: They have BC, Duke, and South Carolina, then the ACC championship game, against, IDK, Pitt maybe? Those are all competent teams capable of pulling an upset, though none of them are what you would call good.
Michigan: Pull Rutgers, Indiana, OSU, then the B1G championship game, probably against Northwestern. Beating OSU on the road would be good, but probably not going to get much cache from the other games.
ND: Gets FSU, Syracuse, and USC. Funny that Syracuse is clearly the best team on that list.