You don't know enough about how any of this works, that's why you can't imagine specifically how it will make things better. We've had USB headphones for many years now, they supply an important niche but there's only so much that can be done with audio. Source -> DAC -> Speakers. Anything else would be software level control, which we already do through many different applications (lowering volume for notifications, equalizers, etc). All of the control, and the improvements that you imagine, have to take place at the software level because once the signal passes the DAC to go to the speakers, it's a done deal. So having headphones connect to a digital port isn't going to provide any more opportunities for advancements and creative applications than we already have. The capabilities you imagine are already here, and have been for as long as we've used computers for audio, and the port has nothing to do with it.