Assuming that current testing equipment can measure the ABR wave-V, it would seem like it would be possible to implement a test like this now. As I said, I haven't seen the paper so I know any of the caveats that didn't make it into the abstract, and I suppose they may have more advanced testing equipment than the typical ENT. (Liberman and colleagues are exploring a number of other approaches as well: http://www.ncbi.nlm.nih.gov/pubmed/26323349 and http://www.ncbi.nlm.nih.gov/pubmed/26657094.)Developing this should not take an enormous amount of time?
Although most of the posts here are about stem cells or gene therapy, I've been wondering how it would be possible to provide the right treatment to the inner ear if you don't know what specifically is damaged. Although it is the "gold standard", we know that pure tone audiometry doesn't capture many hearing issues so would seem to be an inadequate test to distinguish specific types of damage.
I recently came across a paper "Human audiometric thresholds do not predict specific cellular damage in the inner ear" (http://www.sciencedirect.com/science/article/pii/S0378595515302914) where they are able to dissect human cochlea that were preserved at death and compare them to the same individual's previous hearing tests. In other words, they could quantify hair cell and nerve damage in humans similar to the way they do for mice in animal experiments. They found good though by no means perfect correlation between hair cell loss and hearing threshold but essentially no correlation between hearing tests and nerve damage. It's worth nothing that the hearing tests weren't conducted immediately prior to death - median time 2 years - though one was done only 5 hours prior! Thus they don't know test hearing test results that would be most closely related to the state of the cochlea at death.
In addition to non-invasive tests, there's also work on non- or less-invasive imagining. I posted this in a different thread, but it fits nicely here as well:
There is work on imaging techniques to view the inner ear at the cellular level in order to understand what is damaged. See, for example,
http://biomedicaloptics.spiedigitallibrary.org/article.aspx?articleid=1392727
http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1691511
Additionally, at least one attempt is underway to design an endoscope for inner ear imaging
http://www.researchposters.com/Posters/COSM/COSM2015/F010.pdf
If they can get this worked out, it will be a big step forward to be able to correlate hearing tests and patient reports with imaging of the inner ear and to attempt to develop hearing tests that can distinguish inner ear damage.
Much of this work seems to be done by a relatively large group at Mass Eye and Ear and Harvard. It's not as sexy as stem cells or gene therapy but this - along with drug delivery methods - seems necessary to better target therapies.