Any team that stood a chance of being invited to the Big10 (based on pleas) would have left the BE long long ago.
While you are likely right, the landscape is changing and the B10 would like its network to reach more households. I don't think Rutgers adds too many viewers, but UConn would give them competition with the ACC in NE and NY.
However, they are likely holding a spot for ND as an all sports member. That does complicate things numbers-wise.