I have been thinking about this as well. Something sustains this hyperactivity. There are studies which say that malfunctioning potassium channels cause the neurons to stay in a hyperactive state. The restoration of potassium channel function will consequently calm down the neurons possibly resulting in reducing Tinnitus (this explains the effectiveness of Retigabine for some). Considering the brain is subject to plasticity and hence always changing, perhaps this situation can resolve by itself after some (longer) time when potassium balance has been restored, resulting in reduction or disappearance of Tinnitus. Re-exposure to loud sound might prolong this recovery process where at a certain point the recovery-time exceeds the average lifetime of a person (effectively making the condition "permanent").
However, I am not sure about this and have so far not read any research about restoration of potassium channels by itself. So take my blathering with a grain of salt.
Here's a study which concludes that potassium reduces hyperactivity in the case of Epilepsy. We all know Tinnitus and Epilepsy seem closely related, so this might be of interest.
That's a very interesting theory. I wonder if it's possible to get rid of the hyperactivity even when the hair cells didn't heal.. the way I was understanding it so far is that the damaged nerves cause a "glutamate storm" which brings the auditory cortex into an excitatory state... hence that's why drugs that enhance the activity of GABA receptors can reduce the volume of T for some and calm the "storm".
But this would most likely only work as long as you are taking a drug.. but what happens when T naturally disappears? I don't think that this is just a "spontaneous" remission out of nowhere, I mean something has to cause this.
So I think the question is 1) does the hearing loss persist, e.g. the hair cells are still damaged/dead and still the hyperactivity went away on its own for some reason. (the reason for this could be found in your hypothesis?!)
or 2) the damage actually healed naturally and the hyperactivity is going away as a consequence of the healing processes and the now again working "communication", but this processes as this experiment shows, takes some time.