There is a third possibility and one that many here haven't thought of: What if Texas and ND decided in the future that they'd be better off getting together and forming a new conference? They could take Florida State, Oklahoma, Clemson, TCU, Baylor, Louisville, WVU and a few more with them. It would be a conference whose football matches the SEC and may make as much money as the B1G/SEC. You'd have the Texahoma, Southeast and parts of the South and Northeast represented. ND would be able to bring in Pitt and Boston College, schools that they love to play against. It would be as close to a national conference, which would be the scenario that could convince ND to join. The trick would be how many schools could be taken in order to overcome the GoR issue in both the B12 and ACC but that combined conference is already better on paper than either of them separately. Does Kansas go to this new conference or to the B1G if they offer? Iowa State would certainly hope that there would be a spot for them, unless the PAC offers.
Without the football schools (especially if the ND-Texas alliance becomes a reality) I think the founder schools would find it difficult to hang on and that's when you'd see them start talking to other conferences.
I think there is a fourth possibility that you may have not considered: the total destruction of the ACC. I think it may will go down like this.
1. UNC loses it's accreditation and part of the deal to get it back is de-emphasis of their athletic program. UNC drops out of the ACC and levels down to division 2.
2. Needing a team for football while keeping the basketball/Indiana market, the ACC trades ND for Purdue. ND goes full in for football.
3. UVA and Duke, not wanting to lose their connection with UNC, drop down to division 2 as well.
4. VT joins the Big10.
5. Not wanting to help UT in any way, The SEC brings in FSU and Clemson.
6. NCST and Miami join the AAC..
7. UT, OU, and KU see the writing on the wall and join ND in a the Big10.
8. Florida, being upset that FSU joins the SEC, leaves for the Big10, and takes UGA with them.
9. GT goes to the SEC, taking ECU with them.
10. WF, UL, Pitt, BC, and 'Cuse ask to join the AAC, but are denied.
ND gets their relationship with UT, UT gets to part of a The CiC, and The Big10 gets a whole lot of new and upcoming AAU schools.
See I can play this game.