The B12 will poach the AAC before the B12 leftovers jump to the AAC.
TV deal, name recognition, the fact the B12 had P5 status and AAC didn't. That branding matters a lot. Dumping it would be foolish. The leftover over 7-8 B12 teams will expand, take BYU and poach the AAC, and be conference 5. So congrats P12/ACC, you just got promoted to conference #3 and 4!