Both Maryland and Rutgers are members of the A.A.U.-American Association of Universities- a prestigious group of 62 universities that are research orientated. All of the Big 10 schools except Nebraska are members. Part of the reason Maryland and Rutgers got invited is because 1) it opens more financial markets for the Big 10 network 2) they are bordering states to another Big 10 State, and 3) they academically match the rest of the league.
Personally, I think going after Maryland was a payback for Notre Dame going to the ACC.
Virginia is a member of the AAU, but their roots are in the ACC. When VT got accepted to the ACC, the attitude of the program was "we're finally where we belong". VT is not a member of AAU.
Actually, a likely expansion would include Univ. of Colorado- which gives them the Denver media base.