Maybe the new Verizon model will come out every January? Think of all the money that would be made between Apple, AT&T, and Verizon off all the crazy people who would switch between Verizon and AT&T every six months to get the newest model.
You could make a killing on early termination fees. Either that or you would have folks walking around with 2 iPhones (one Verizon and one AT&T). You would not be considered a true Apple Fan unless you had one of each.