Well, they found the chemicals that translate vibrations into sound. And it wasnt confirmed on humans, but on an animal whose ears are closely similar to humans.

So theres a long way to go. First they probably need to confirm the same hypothesis on humans. Then they need to see how it is related to the inner hair cells. So were probably looking forward regenerative hair cell medication. When a medication is found, it will need to go through all clinical trials. So overall I'd say 10 years if we are very lucky, otherwise 20-30 years.