They could just use the sub-mini 2.5mm audio jack and plug instead of the 3.5mm. Quite a few phones do/did.
The use of the 3.5mm was widely applauded for its compatibility when the iPhone was released. I can't imagine they'll take any decision to change it lightly, and a transition path will be on their roadmap.
Assuming that this is true (which is a Godzilla-sized assumption), why are Apple again walking headlong into a autumn release fest. Surely it makes more sense to stagger releases of your product line throughout the year, rather than have one super heavy period?