And given that usb-to-3.5mm adapters already exist, I assume that if this happened, the appropriate adapter would appear on the market fairly quickly, so you could keep using your old headphones.

So now I have this ultra thin cable going to the phone in my pocket, but next it will have to be a whole USB adapter - I'm really not looking forward to that.

At the same time - sure, Intel should go ahead and implement this. But phones should just have both USB and 3.5" connectors.