there has also been talk of Texas going independent. they are a beast in several sports and could likely pull off their own tv deal and make much more than they do in the big 12.
andy yes, the tv revenue shared by all big 10 teams dwarfs that of the big 12 (hence any interest texas might have).
football goes in cycles for most teams. right now, ohio state is up and michigan is down. it is not always like that. Tressel does a very good job, but wont be there forever. once UM gets the "right" coach in there, there is no reason they cant hang with OSU. no doubt though, recent history indicates Texas would be king in the big 10 for the time being.