First, I believe that any school that would accept a partial payout to join the Big Ten isn't good enough to join today's Big Ten.
Second, CBS/NBC/FOX, the big money, have 3 primary games and the Big Ten have I would say 4 top tier schools USC,OSU,MICH,PSU, plus other matchups between whoever is good in a certain year. I don't see Clemson, Oregon, FSU, or whoever being so good that those networks would pay more money to add them. They aren't a tier above the current conference inventory.
Third, the Big Ten has inventory of 7-8 conference games/year with byes with 16 teams. Likely 1 game for CBS/NBC/FOX, a Big Ten Network tripleheader, then the last 1-2 are flexed between Fox/FS1. If you add more teams, you'd need to either get another FS1 timeslot, which Fox already sold to the B12, or use BTN overflow which I don't think anyone wants to be on.
Fourth, there is still money out there that the Big Ten and SEC don't monopolize which is the college football playoff. I can't see more expansion unless the Big Ten and SEC breakaway with the remaining few power schools, form a NFC/AFC type schedule, and crown their own champion with their own playoff. NCAA tourney can stay the same.
Fifth, UCLA/USC travel is their problem. Adding a team in Eugene or Seattle is still really far away for everybody, and quite a few sports like cross country, track, swimming you can just travel once for a conference meet if you want to.
Sixth, the top tier schools will break away and form their own new conference before anyone gets kicked out or relegated.
Seventh, media markets only mattered because of the cable tv bundle. And the cable tv bundle is collapsing more every year.