I don't think 4 x 16 = 64 is a given, and besides reasons already expressed, there are some other contrary precedents.
You have the present bowl system to contend with, the highly popular NCAA basketball tournament that expanded beyond 64, as well as older and more traditional teams like Iowa State that bring something to the table and some would say a lot except TV sets, and some fast growing and some enormous newer colleges in faster growing urban areas. Even if you look to professional sports as the model the leagues have expanded over the years.
If you forget institutions and specific facts and look at things in larger historical terms, what sucks about possibility of losing Texas, the state, is that it is obviously the largest and fastest growing state in the middle of the country, bar none. The possibility was/is there for ties that bind the giant mid-section together, instead of driving everything towards the coasts.
To say it has to be 64 and 4 x 16 smacks not only of a for-profit enterprise, which I am not necessarily against except it ought to be treated as such, but also a cartel. And not just any cartel, but given that many of these are ostensibly public institutions, a government created and officially sanctioned cartel even if just implicitly, more difficult to displace.
If it is going to be run like a business there may be business reasons for more than 64, if not right away, though I believe there are, then certainly in the future.
I have no idea what is going to happen.