Something similar can be done with USB. If you look at the USB type C connector specification, you'll notice that it already defines one alternate mode in its

Something similar can be done with USB. If you look at the USB type C connector specification, you'll notice that it already defines one alternate mode in its single appendix: a headphone alternate mode. That is, with the correct hardware in the phone, and a passive USB-C to 3.5mm jack adapter (also described in that appendix), new phones from other manufacturers which use the type C connector would be able to follow Apple's lead and drop the headphone jack. (And in case you were wondering, that alternate mode can charge at 500mA and connect to the headphone jack at the same time in a single USB-C connection.)