For what it's worth, this whole expansion deal initially revolved around Notre Dame (and I'm just a fan, so all this is speculation).
You guys became available once all the discussions and posturing started, and emerged as a total no-brainer fit for the conference. I don't think people were thinking of you guys early on, because at that point, it was still possible that we were going to 12 teams total, and that one team would have to be Notre Dame.
But once it became inevitable that some conferences were going to crumble, you guys make total sense. Notre Dame makes total sense.
Texas makes a lot of sense, but they have some extra political baggage that needs to be dumped, and they also need to know that they would join the Big Ten as an equal member, something they haven't had to deal with in the past. Texas might be a HUGE school from athletics/revenue/TV market/etc perspective, but rest assured, the Big Ten is so stable that adding Texas just makes sense; the survival in no ways depends on that though.
So you guys are in, Notre Dame is ASSUMED (because...if they don't, this whole shakeup is going to be questionable). If Texas comes, they might have to drag aTm with them, and that leaves one more spot. That spot could be any of Missouri, Syracuse, Rutgers, Pitt, Maryland, UConn, or Kansas.
If Texas DOESN'T come, then that's three open spots, and then it could be any of the names mentioned above.
Should be an interesting few weeks here (pieces should start to fall in place quickly though, at this point).