ND is essentially a member of the ACC and will soon have to add they 4 additional football games to make it official. That takes the ACC to 15. I don't know who will be #16, but I will be stunned if it is WVU. West Virginia is the third world equivalent for the region and VA & NC people are not fond of the West Virginians.
The SEC is more obvious, the Oklahoma schools. OU. OSU, TAMU, LSU, MSU and Ole Miss fit very well together.
That would send tremors through the Big12. They would be desperate for teams with a market or name brand.