About six or seven years ago, there was talk that Missouri would join the Big 10. I'm not sure how I would feel about that-the plus side (selfishly) is that I would get to see my Tigers much more often since Chicago is ground zero for the Big Eleven. However, I like the Big 12, the rivalries, the wrestling, and messing with Texas.
As for other teams, just thinking about Illinois, Illinois State is D-IAA, so they couldn't make the jump to D-IA and the Big Ten in one year. Northern Illinois, however, is part of the MAC, has a strong football program, and a full slate of sports that the Big 10 sponsors, including wrestling. They already play Big 10 programs (NIU is opening football season against Iowa at Soldier Field, and later plays Wisconsin in Madison.) They're on television all the time, and they also have an incredible AD who could make a jump to the Big 10 happen. This is purely speculation, but Northern Illinois would make an excellent candidate.