I just don't see us getting an at large bid if we don't even make it to the Big 10 Championship game. The SEC has three teams in the top 10 of the BCS, Big 12 has two, ACC has two, and the Pac 12 has two. Big 10 has zero, and the Big East has zero. There's still enough season left for this to change, but I don't give us a high probability of making one right now.
Most of this really isn't relevant though. What is relevant is how many non-champs get automatic bids for being in the top 4 (almost certainly Alabama), whether a non-AQ team gets in automatically (pretty likely to be Houston, TCU or Southern Miss), and then it's just who else is in the top 14 and is attractive to bowls to fill the other two spots The Big 12 loser probably takes one. The other is between us (IF we make the top 14) , Stanford, the ACC loser or Boise to fill the last spot. Bowl selection order makes a huge difference here. Since the Fiesta gets the first pick, they aren't going to take the unbound Big East champ or the ACC loser. Stanford? maybe. Boise? doubtful. Nebraska, especially vs OU? Seems like a winner.
Still plenty of games left that could shake things up, and of course the #1 thing is for us to win out, and win the B1G championship if we get there.
You want the worst scenario? LSU loses the SEC championship, Oregon loses again, and OU or OSU loses this month but wins Bedlam. That probably puts LSU vs. Alabama in the championship, and Georgia goes to the Sugar Bowl. That's the one way a conference gets 3 teams in, and it takes away the spot we'd be shooting for.