Researchers have published an article in Nature showing that they can store 1.6 TB on a single disk.
While this may sound like a lot of data, its not compared to other modern media formats. LTO4 tapes are capable of storing 1.6 GB (compressed) and LTO5 tapes are due to store 3.2 TB of data, on a single tape. 1 TB S-ATA drives are now common place and a 1 TB 2.5 inch solid state drives have been around for a while now.
What makes this 1.6 TB optical drive interesting is that it will be very cheap media.
Optical media is very cheap to mass produce and historically the drives burners and readers become very cheap very quickly. While tapes may be cheap, the tapes drives are not, and hard drives which are mechanical are not very cheap either, when compared to a CD or DVD.