I don't think this is very likely at all, if you look at the phones as an example they will keep the same case for 2 generations as least.
Once they pay for all the machinery and setup to makes cases and straps a certain size making them the same for an extra year at the scale apple produces probably saves them a ton of money.
I thinks this is why the phones have the same casing for 2 generations, Apple simply makes more money that way.