I think this is the key difference between this year and last year. For all the talk last year, nobody went past 12 teams, and the Big East and Big 12 were left in some viable form. With the move of aTm to the SEC, this is a whole different animal. The SEC won't want to stay at 13, so they either need to move to 14 or 16. Those additional teams will come at the expense of the Big 12, ACC, or Big East. The Big Ten will look to respond and also expand to 14 or 16 to make sure they can get their picks, and at that point the Big 12 is history so the Pac can swoop in and move to 16 as well. Where exactly ND ends up here doesn't really matter.
That leaves ND moving into a super conference where they don't have near the power and independence they could get from moving to the Big 12 today. This is the most independent long term option they have. A strong Big 12 with ND, BYU and a third is not going anywhere, and neither are any of its members. Without the Big 12 collapse the Pac has nowhere to grow, and it would seem a lot less likely that the Big Ten goes to 16 either. In this case, you may only see the SEC go to 14 by poaching the ACC, the ACC steals one from the Big East to stay at 12, and the Big East ends up right back at 8 where they started. ND keeps the NBC deal, launches their own network, and we setup a 7 game schedule to give them flexibility, and maybe find a way to assure an annual matchup with Texas with protected rivalries or something. For their other sports, they get a decent upgrade from the Big East.
ND has the option to dictate their own endgame here and protect their own interest right now, or have it dictated to them in a few years. The only way I can see this shaking out without ND being forced into a conference is if Arkansas comes to the Big 12 so that neither the Big 12 or the SEC needs to add any other teams, and I see no chance of that actually happening.