You are indeed correct. Right now there are four teams tied for third place with 11-6 records. If all four win (MSU @ IU, OSU @ Wisky, Iowa at home against NW, and Purdue at home against Illinois), MSU would be #3, Iowa #4, Purdue #5, and OSU #6.
But, if OSU loses at Wisconsin, the tiebreakers for the remaining three 12-6 teams change and we'd jump Iowa for the #4 seed.
If IU beats MSU and OSU loses, we'd jump to #3 with Iowa at #4.
But, if OSU wins and MSU loses, we'd be back to a #4 seed with Iowa at #3.
So, we need to win and have OSU or MSU (or both) lose to get a double-bye.