Right now, we're in perpendicular territory, with areal densities under 1Tb/in². Shingled magnetic recording has already appeared in datacenter drives optimized for cold storage. Along with two-dimensional recording, a similar and potentially complementary approach, shingled tech looks poised to drive density scaling until at least 2017. That's when heat-assisted hotness is slated to take over, the crystal ball says.
If the ASTC's projections are accurate, heat-assisted and bit-patterned recording will combine around 2021, pushing areal densities up to 10Tb/in² by 2025. In a four-platter consumer unit like Seagate's Desktop HDD.15 4TB, which packs only 625Gb/in², that density would theoretically fuel 64TB of storage. Well over 100TB would be possible with a seven-platter monster like HGST's enterprise-oriented Ultrastar He8.
Source: The Tech Report