Hockey is one of those sports that you might have a good argument for leaving those teams where they are at, and if Nebraska, or anyone else decides to play hockey, they could do like they could have done all along and apply to join a division. Then again, the Big Ten could look at it and see there is more money to be made by creating a Big Ten conference for Hockey...and capitalize on the television revenue.
I dont know about the other schools, but Gopher hockey games are televised, and while most of the games are on FSN, there are a several on the big 10 network. So creating a big 10 hockey division likely wont mean more revenue for Minnesota's hockey program, and, anyways, Minnesota actually makes money off of its hockey program. I know its the same for Wisconsin, and probably Mich as well