As long as TCU beats Texas, I only see one scenario where we don't make the Big 12 title game if we win out. TCU & WVU would both need to beat OU. That would be TCU with 1 loss and us tied with WVU. Other than that, We'll either be in a 4 way tie with WVU, OU, TCU (where ISU & WVU would make it due to both being 2-1 in round robin) or a 3 way tie with 2 of those teams in which one of those teams would be 0-2 (not us).
The 3 way tie would be for 1st with TCU or OU and WVU (we'd play WVU). Other scenarios lead to a tie with TCU or OU for 2nd (which we would win).
*I may have missed a scenario, but this is what I figured out in the last 15 minutes thanks to Excel.