Is 16 a worse number then 14 if by some miracle ND does come on as a full member down the line?
Not necessarily.
There's an interesting thought on shaggybevo about 4 pods of 4 teams with two rotating designated rivalry games every year. E.g., Team A from Pod 1 plays Pod 1 teams (3 games), Pod 2 (4 games), Rival B from Pod 3 (1 game) and Rival C from Pod 4 (1 game).
In real terms assume that each Pod has an "anchor" team (FSU, TX, ND, OU) and that those teams are permanent designated rivals. That way no matter the rest of the schedule you get FSU/TX, FSU/ND, FSU/OU, TX/ND, TX/OU, ND/OU which is a lot of must-see television. You also get 8 anchor / second fiddle games per year and everyone plays everyone else at least every 3rd year. That's workable and would serve up a ton of great games so long as the conference didn't mind moving a bit away from traditional scheduling.
Which isn't to say that 16 team conferences are inevitible, merely that they could be made to work. The inevitible question the true top shelf programs will ask themselves eventually is, "Why do we need to drag along the Kansas States, Iowa States, Northwesterns, Washington States, etc. of the world?" Check back in 2025 (-ish) for the resolution.