I agree, I see this ending 1 of 2 ways.
1) Colorado jumps (I think they'll be the first) and Arizona, ASU, Utah, WSU and OSU will try to follow (Big 12 will most likely not take all of them). At that point, the Big Ten will either have to add some PAC schools or risk them going to the Big 12 and having their GOR locked up for longer than desired. My guess is the Big Ten would add UO/UW at that point (Possibly Cal/Stanford as well).
2) Colorado threatens to leave and UO/UW aren't that confident that the Big Ten would invite them under scenario 1. The PAC 12 signs a short (3-4 years) deal to keep the conference around a few more years.
I think it will probably end up being scenario #1 because I don't see the incentive for Colorado to go down the #2 path unless they really think nobody in the PAC 12 is ever going to end up in the Big Ten. And based on what's out there, I don't see how you could come to that conclusion.