If OU beats OSU, I think OU and OSU could be in the BCS. However, if OSU gets passed up by the BCS, Cotton will surely pick them.
If OSU beats OU, a two loss OU team gets picked by the Cotton Bowl, IMO.
Unfortunately, I don't really see how we get into the Cotton unless we win out and BOTH of the Oklahoma schools go to the BCS. 
If OSU goes to the NC, wouldn't OU go Fiesta?
No, jfc people...the big 12 is not guaranteed two spots and another OU loss could have them on the outside looking in. OU beating OSU is our best bet at securing the Cotton.
Assuming that 2 BCS spots go to Stanford (or 3 loss ND team that beats Stanford) and Alabama, please rank the following teams and tell me what 2 teams the Fiesta, Orange, and Sugar would pick over a 2 loss OU team:
a) 2 loss VaTech or 2 (or 3) loss Clemson (outside BCS top 10)
b) 2 loss BigTen team that didn't play in their CCG (currently outside BCS top 15)
c) 1 loss Boise St (outside BCS top 10)
d) 2 loss OU (currently BCS 6th and wouldn't drop out of BCS top 10 unless blown out OSU)
e) 3 loss BigTen CCG loser.