If ESPN opts out, I can't see them shelling out whatever it is to get whichever schools they want in the SEC, losing a few schools to the B10, then turning around and giving the leftovers a deal on par with what they had (and on par with what the B12 has). I could see two factors, though. First being the GOR. It's unclear if the GOR is dead if ESPN kills the media deal, but they might want to come to an agreement to skip having it tied up in courts (also, paying to fight it in courts and potentially losing). Second, how much of a threat are the streamers and how much does ESPN want to keep them out? Schools are resistant to change, and it would be considered a win to stick together as long as they can keep pace with the B12 money-wise.
I see two levers the B10 could use to try to push Notre Dame, one being absorbing a big chunk of their traditional rivals. In addition to Mich, Mich St, Purdue and USC, the B10 could add Stanford, Miami and/or FSU. The B10 could play dirty and limit the opportunities to schedule member schools, kneecap the ACC and basically make life difficult for ND.