The only thing I worry about at all is access to the playoff. Personally, I will start getting nervous when the Big 10 and SEC start looking to add multiple teams that don't really seem to make sense from a per team media value perspective, and between the SEC and Big 10 they get over 40 members.
For now I think ESPN and Fox both understand that cutting off a chunk of the plains (low population by very high interest in CFB), Washington, Northern CA, Arizona, CO and Utah from the playoff would jeopardize growth. None of these areas are absolutely critical, but all of which, they are either high population or high interest. All together it starts to matter. Bigger pieces of the pie for those that remain, but cutting those areas out limits how much that pie might grow in the future. I think football growth rate is tenuous. I don't think we've seen the hit that the massive decrease in kids participating in football will eventually have.
If the Big 10 adds Oregon, UW, and say Stanford, with a spot open for ND, while the ACC starts to take steps toward dissolution with UNC, UVA, FSU and Clemson all Big 10 or SEC bound, I'm starting to get worried. Then you might see a couple Big 12 brands poached. That's why I would rather see the Big 12 get aggressive, add the four corners schools and make a push for UW. I don't think the Big 12 can sit looking to optimize media dollars per team. The conference needs critical mass and enough critical geography locked up to help stabilize the conference and playoff access.
That also suggests to me that the Big 12 better be careful if they stray from ESPN or Fox in media deals. Like it or not, if you sign a decent media deal with one of those two, the Big 12 becomes a co-product of one of the P2, and that media partner becomes motivated to keep the Big 12's playoff access. If you sign outside of those two, they probably push the P2 to poach enough to blow up the remaining leagues.