I can offer an opinion, but I must give the disclaimer that I only have one year of law school under my belt at this time. Without speaking on the legal terms b/c contract law is far more complex than about what is only written in the document (i.e. parties intentions when agreeing to a contract, which is incredibly hard to discern without an actual factfinder which means actually pursuing litigation), odds are Nebraska will pay some sort of penalty, but it will not be anywhere near the amount spelled out in the agreement.
Litigation is stupid crazy expensive and neither the Big 12 nor Nebraska wants it to come to that (lose lose) lawyers will settle out of court and neither party will be satisfied, so are legal disputes. In the end Nebraska will not pay the supposed 80% penalty (or whatever absurd number it is), but will pay something to make it go away.
I can't say 100% that it won't go to trial, but it is extremely rare for that to occur, especially in a situation such as this.