The idea that it will never happen when many schools have been or still are at a lower payment, is a bit over optimistic.
It would not take much for them to move to a permanent uneven revenue model. Nebraska just got a full share in the last few years, after how long? Maryland and Rutgers are still reduced after how long? Oregon and Washington are extremely reduced....for how long? I am not even sure they have an end date. I believe the speculation/hope is they will get a full share or possibly just an increase in the next contract.
I hate to say it but in the future the only hope for some teams to stay in the B1G may be to take a reduced share. The big boys are happy to give everyone the same...minus any new teams, as long as they keep getting a huge bump in pay at every contract. But what happens when those huge bumps start to disappear. Disney, ESPN, Fox etc are struggling with money, They are trying to back out of some contracts. They are making back door out clauses in contracts. Some day it might come that the B1G gets little to no bump in their media contract, possibly even a reduction. The schools at the top may not want to take that hit, they may say we bring all the value and Northwestern doesnt. At which point they might say take a reduced share or go somewhere else.
Not saying it WILL happen, but I would not say it will NEVER happen.