On the issue of hearing I think eventually this will become bypassed completely, the same technological jump from analogue to digital will be from digital into analogue then digital will be shrunk to digital only.
That probably doesnt make sense but I think its inevitable we'll have bio implants which speak the digital language of our brain's neuron and transmits the same information into your brain as an organic ear does now.
Given the plasticity of the brain, chances are you'd not have to actually understand how the brain understands sounds, it would be the brain which learns how to understand the electrical signals transmitted by the electronics.
Such prototypes have been around for years, so I just think its shrinking and tuning.
Similarly with vision.
Then the output similarly, instead of you having brain signals leading down the nervous system into muscles which use chemical energy to move muscles which via tendons to bones move joints, to tap on a phone screen an alphanumeric word, you'd just think it and it would be electronically transmitted. Then you don't need to speak or move, just think.
As of 2018 we've removed the digital-analogue of the phone DAC to output a variable voltage and current into a phone signal, now into it staying digital up to just outside your ear drum where its made analogue in the last millimeter. I just see that digital path getting nearer and nearer to the brain.
Initially these would be used for medical reasons - to overcome profound deafness, blindness, amputees, paralyzed, etc. But given this can augment and boost the spectrum, it would become a financial gain to the individual in terms of being a faster more efficient human. Then once it allows for safety advances then then becomes mandatory legal in certain job types and then eventually just mandatory for everyone and likely inserted at birth. If I had to guess that whole journey, I'd say 200-500 years.