I have to plead ignorance on what the set-up the various conferences have with the networks, but do you think that the Big Ten and Pac Ten, by virtue of no divisions and thus more excitement at the end of their regular seasons, make up some of the difference by season ending revenue games like Michigan-Ohio St and UCLA-USC that the XXII and SEC can't duplicate????
Possibly. It was a foolish decision to end the annual nature of the Nebraska vs. Oklahoma rivalry; Surely the Big 12 would love to see that played right before/after Texas vs A&M. Then there's Alabama vs. Auburn. After that, most of the great rivalries are interconference and thus cannot replicate for one conference what UM/OSU does for the Big 10.
Then again, that rivalry game is one of the great paradoxes (using this correctly?) of the college game; The game is big because the history and size of the programs involved has made it so, but in order for it to stay so prominant the rest of the conference must always be subordinate to this order. The likelihood of a championship game payday and greater appeal for other Big 10 schools is limited to what the conference will allow without overshadowing this game.
In that sense, I view the rivalry kind of like Notre Dame, a great tradition that might have to make some sacrifices for the betterment of the game overall. I don't suspect the rivalry would suffer if the conference went to 12 and had a championship game, in fact that act might save the rivalry when their records aren't as good but a championship game berth is on the line.
With a championship game there's always a reason to pay attention, whereas some years a rivalry game may have only that tradition to offer.