The 12 team CFP moves the cut line lower, and in doing so lessens the relevance? of late season matchups between undefeated or 1-loss teams. Everyone recognizes that, which is why there's been ongoing discussion of discontinuing conference championship games.
But Texas has had exactly 5 seasons with only one conference loss since the inception of the Big 12 in 1996. in each of those seasons, the single loss was to ou, not aggy. Tack on the two undefeated regular seasons of 2005 and 2009 and the Texas has found itself in a position where a rivalry matchup would have less meaning under the expanded CFP a whopping 25 percent of the time.
I love everything about our current trajectory and the incredible job Sark has done across nearly aspect of the program. But there is no evidence based on the relatively similar current postures of ou and aggy to suggest one rivalry game relative to the other has lesser (or greater) importance going forward. Rather, the more likely long term effect of Texas moving into a much more difficult conference is that all of our rivalry games - ou, aggy, piggy - actually increase in importance because having 1 or 2 losses in conference play would put us at or near the cut line.
The good thing is the games will be played and all of these various hypotheses will get tested against actual results.