'Bama-Tenn and Auburn-Georgia. It was those 2 rivalries that forced the SEC to implement the protected cross-division games in the first place. Originally it was 2 protected and 1 rotating, but a few years later flipped to 1 protected and 2 rotating. I did read somewhere when the SEC was deciding who goes in what division, it wanted to make sure that both divisions had an equal number of the brand name programs.

At the time the SEC had 4 that qualified; 'Bama, Florida, LSU, and Tennessee. Although some people in the SEC wanted to include Auburn and Georgia on the list. Hence why 'Bama and Auburn were placed in the West instead of the East with Tenn and Georgia. It is reasonable to assume that if the SEC decides to re-align the divisions at some point, then it will try to maintain that balance in name brand programs.

The SEC can't simply maintain the current divisions and simply add 1 or 2 more teams to each division. If the SEC adds 1 and keeps the conference games at 8, then the only cross-division game for each member is its protected cross-division partner. If the SEC expands to 18 and goes with a 9 game conference schedule, then it will end up with the same fate. If the SEC is going to expand, then more pressure will be placed on making sure the 2 AL schools are in the same division with Tenn and Georgia because it can eliminate the need for a protected cross-division game.