They changed their charging port once since the release in 2007 and they made one other connector change (removing the headphone jack) during those 15 years.
They also had three revisions of SIM in that period.
I'm not saying I'm not 100% on board with these changes; I'm saying that it's silly to depend on another company. because even the flagship product which is very mature will either change or be discontinued quite easily.
The whole industry also went through the same sim revisions. (And, with eSIM, there are now four revisions.)
iPods are still available:
I’m sure someone said this same thing about iPods once.
I haven’t seen a new iPod in years.