If & when the SEC goes to 9 conference games (B1G has been at 9 conference games since 2017) and if a regular season scheduling agreement is made with the B1G consisting of approx. 12 games played between the SEC & B1G annually, then Notre Dame is going to have a more difficult time scheduling premier opponents. The Irish will probably need to schedule a few Big XII and PAC 12 games each year... NBC will not like this and I could see NBC start to pressure Notre Dame into joining the B1G in all sports, including football.
If Notre Dame does eventually join the B1G, then NBC will probably try to work a deal with the B1G to retain broadcast rights to all Notre Dame conference home games, with FOX & CBS splitting the Notre Dame conference away games.