The slab of glass has about the size of a CD case and despite having less capacity per slab, the storage volume for a given amount of data would be about half of what would be needed now with the biggest HDDs and similar to the volume required by tape cartridges.So the density is already good enough.
The main problem is the cost of the lasers used for writing, which would have to be reduced for mass production. The second important problem is the writing speed, but there also the cost of the lasers is the main problem, as for a greater speed more lasers can be added.
Despite the current writing speed being similar to downloading files from an Internet source that throttles you, I would be quite happy to have such a device, even with its current level of performance, to avoid worrying about having to pay periodically for new HDDs or tape drives, in order to migrate data from the old HDDs or tape formats.