I think (I hope) that the Big 12 schools are scheming furiously to find P4 homes for all members, so that they can euthanize the conference. Though I believe their efforts will be for naught.
Here what I envision: Whichever of B1G or SEC lures Oklahoma will be the big winner. If OK St is tied to Oklahoma, the SEC will likely prevail in the tug-o-war and add both of those schools. If Oklahoma can move without Ok St, then the B1G may win out and invite Kansas as the second school. The other of these two conferences will remain at fourteen. The PAC 12 and ACC will stand pat.
Apart from Texas, the Big 12 inventory does not add value to a thriving P4 conference. So what about Texas? They would sooner choke to death than follow A&M to the SEC. The LHN is problematic in a B1G conference move (not impossible, but messy and expensive). They will gather enough G5 schools to resume operation of the Big 12. The risk for them is that the TV networks, though they love Texas, will not want to pay P5 money for the P5 pretenders that Texas may have assembled. If the New Big 12 cannot get a legitimate P5 media deal, then Texas may approach the ACC and ESPN to take them in. The ACC should assume the position of power in this negotiation. Texas is out on a limb. Any second invitee should be totally controlled by the ACC. The ACC does not need this deal. Texas and ESPN need it. The remnants of the Big 12 would be set adrift.
There will not be a collective effort to arrive at 4X16 or 4X18, or any other symetrical configuration. Each conference will grow or not grow depending on what brings them to their optimum individual state.
By the way, if KSU, TTU, Houston and New Mexico make the PAC a loser, why would they do it?