I think with the size of USB-C and Lightning, we are pretty close to the point (if not there already) where structural limitations are not going to let us go much (if any) smaller. No one wants a connector that will break after 10 uses.
USB-C, electrically, has enough headroom that performance should not be an issue for a very, very, very long time. Already you can push more data over a USB-C cable than a phone can meaningfully handle.
The only thing that really comes to mind is we could go to fiber core for crazy data speeds but those are so delicate I don't think the improvement would be worth the hassle unless we have a big improvement there.
I think C could easily adopt a fiber, there's the "tongue" bit in the middle of the socket, and empty space in the middle of the plug, could easily have a fiber run down the middle there.
iPhones don't even ship with a charger anymore and they definitely did not lower their prices when the decision to leave them out. It's a win-win for them – they can claim to be more environmentally conscious etc. while reducing their BOM cost.
Apple and other phone companies don't depend on selling cables and chargers. If they did, they would have been doing a much better job and they'd be more like Anker and Griffin.