That would never happen because you don’t have any interconference matchups.
Who cares? The NFL isn't doing smart things because they don't have to do smart things. They print money no matter what they do.
Letting Zip Codes decide playoff positions is fine by them, because it keeps people arguing on talk radio all spring/summer.
They don't even need divisions, period. The whole reason for NBA, NHL and MLB divisions are getting more games starting at 7 pm local time on a Tuesdays. NFL doesn't have that issue because all TV contracts are national, and all the games are at 1 or 4 (or the exclusive windows).
I think we covered this before, but the NFL has the least reason to expand because their TV deals are all national and their TV time slots are essentially maxed out anyway.
Adding MLB, NHL, NBA teams create inventory to sell to TV. Total local TV revenues go up.
Nationally, you have two new cities who now have teams, and national TV pays more for that.
With football, the networks are paying for 1.5 games per Sunday, at 1 pm and 4 pm, providing regional coverage to the entire country. All you're doing is changing which game the region gets. That's why the NFL went so long without a team in LA (and why teams actually left LA to begin with. In the other sports, leaving LA -- as a team or leaving it open as a league -- is financial suicide. It just isn't for the NFL).