Companies like Apogee are currently making high quality Lightning compatible headphone amps that charge iOS devices http://www.apogeedigital.com/products/one-dac.
Apple announces Lightning-enabled headphone standard in WWDC session - Page 2
In no universe would it be sold separately.
Ethernet ≠ headphones…
1. in the hierarchy of importance of use
2. in a world in which Apple removes the 3.5mm jack from the iPhone
There you go again. Apple has shipped such things plenty of times.
You’ll have to refresh my memory in this regard. To what adapter are you referring?