I'm aware that hard disk capacity follows a trend similar to Moore's law in that capacity roughly doubles every two years or thereabouts, but much like the CPU industry, does anyone know how far into the future magnetic storage will continue to scale at that pace?
I don't work in the industry, but I did a bit of research on this recently. As I understand it, we're currently able to get several hundred Gb/sq. in. (bits, not bytes) with the perpendicular recording that we've been using since about 2005. Back in 2009, experts were predicting that perpendicular recording as it operates now would probably not be able to exceed 1 Tb/sq. in because of the interference problems at that density. Some of the major drive makers are pursuing alternatives and/or extensions to current recording technology. A couple of the major ones are Heat Assisted Magnetic Recording (HAMR, aka TAR), in which the physical/magnetic properties of the recording surface are altered with heat from a laser or other heat source, and Bit Patterned Media (BPM), in which bit boundaries are actually delineated using non-magnetic material (as opposed to the uniform recording surfaces of today). There are others like Microwave Assisted Recording and Domain-Wall Assisted Recording, but it sounds like these are less likely to be used, at least at first. Recently, there was also a story on Ars Technica describing an effort to combine HAMR and BPM in order to overcome some of the shortcomings of each. Common predictions seem to be that these new technologies would move the density limit up from about 1 Tb/sq. in. to something more like 10 Tb./sq. in. The growth rate has been in decline during this decade, despite the adoption of perpendicular recording, but the hope seems to be that it might rise back up to how it was in the 90s with the next advancement.