To box out the B12 and ACC, so I just don't see that happening. Sure, the SEC and B1G will largely rule CFB, but there will be a place for the B12 and ACC in the highest tier of CFB.
I think on-balance, the death of the P12 is overall better for the B12 than many of the alternatives. The B12 picks up 4 schools from a dying P12, further establishes itself as #3 in the CFB ranks, and #1 in CBB, and lives on.