As the density increase, what's the impact to the reliability of storage. Does the leakage in SSD and maintaining charge in a magnetic disk become a stumbling block?
For some kind of data, the demand of storage may be offset by cloud computing. The future of online storage may be bright. I believe Dropbox would be more interested in GB per Wattage than density of a harddrive.
With more people storing more audio and video, methods to store more efficiently and economically are becoming more critical than ever. I'm not sure that this will actually be able to meet the demand but should certainly help.