Well, we used to call that ‘a saturated marketplace’.
If you at Apple still think you can sell more ice to more eskimos, then go for it!
The Eskimos will eventually be forced to upgrade to 5g handsets.
I know AT&T customers that were given a new iPhone for free, to move the customer off of their 2g/3g network.
Want an Apple Watch? You’ll need a new enough handset to setup & upgrade the watch.