You have Arkansas, Oregon and Bama coming up for your non-conference schedule over the next few years so I can at least see why you wouldn't want to throw OU in the mix. You at least have some legitimate teams to prop up your national reputation outside of the Big 12. I do have a feeling that you're going to want that game back eventually. Maybe not now as much since you can claim eternal scoreboard after losing 85% of the games over the course of the series, but at some point you are going to look up and realize that the biggest game on you schedule is... who, exactly? KSU? KU? ISU? Colorado? Tech?
We walked away from the A&M game with the same, "You left this conference, go fuck yourself," attitude. I think they were stunned that we would end it, but after a few years, we were the ones that started calling them out for being big pussies for not rescheduling it. The didn't want it when they could hide behind the SEC logo and say how much better they were without ever having to show it on the field. In the long run, OU needs that game much less than you do. I think you would be better off trying to keep it, but I get where you're coming from.