Since ND is playing Georgia next year in Athens, I would like to think that if they win that one, they should take care of the rest of the teams on the schedule since GA is by far the best team we play.
So if ND is undefeated with a win in Athens, I would imagine they would still make the top 4. Especially if GA goes 12-1 and wins the SEC. It's a no brainer at that point. I would say the same thing for the years Clemson is on the schedule.
However, if UGA were not on the schedule next year and we were playing let's say Sparty or PSU. I say they would be left out. ND is gong to get punished moving forward because of 12 and 18. The losses were just too embarrassing.