I have never once heard any representative of any conference or school say they wanted or planned on having 16 team conferences.
I think that is a number fans and media members came up with because the human brain has a predilection towards equal/even numbered entities.
I don't believe there is or has ever been a perfect or final conference membership number for the big 10. Right now they have 14, but if they can expand into new markets and sell their network to new viewers, thereby causing the amount of money each member earns annually to grow, I believe they will continue to do just that.
I believe they are expanding in phases, getting the conference acclimated after each step before moving forward with new territory. First they started their network, then they brought in Nebraska to get to 12 and form a championship game, then they jumped into some giant tv markets by bringing in Rutgers and Maryland.
Now, I believe they are waiting before going after UVA, UNC, Duke, GT, FSU and Miami.
They said they did studies on population shifts and those indicated a shift to the south.
You have four new states that bring roughly 46 million potential viewers for the B10 Network and six schools with brand recognition all then theoretically a part of the B10, which by the way would then have 20 schools and would not only be the most influential voice in college athletics, but would also control the OVERWHELMING majority of all research dollars pumped into public research universities in the world.
Just keep in kind you have never heard the B10 say they wanted 16 members as their goal. That is something the Brad Edwards-types of the world claim to give the impression they are "in the know."
As for the SEC and P12, they will take their choice of teams, too, from the leftover ACC and B12 schools, and will be just fine, but they will be playing catch up forever to the B10.
Just my opinion anyway.