SEC also apparently reached out to Ohio State, Michigan, Clemson, and Florida State. Not sure how much traction that got. Rumors in Ohio were that the SEC teams didn't want to play conference games up north in the snow and wanted them to be on neutral sites which was a non-starter for Ohio State.
That said, I wouldn't be surprised to see OSU/Michigan leave the Big Ten or the Big Ten to also go bold and try to get Clemson/UNC and/or USC/Oregon into the conference.