The HDD market has seen a lot of consolidation over the years and now there are only two major players left; Seagate and Western Digital. Both are active in the SSD market but they're also still developing new HDD technology.
It appears the next big step for the industry will be the adoption of 10 platters for conventional disks. The Register says 10 platters will give us up to 20TB HDDs by 2021, while HAMR and MAMR technology may be delayed to 2022. At the moment, the maximum number of platters used in conventional disks is nine.
In the meantime, disk manufacturers could add capacity by bringing 10-platter drives to market. An 18TB nine-platter drive would then become a 20TB 10-platter product, assuming no increase in areal density. All HDD manufacturers continue to assess backup plans for such 10-platter drives, Trendfocus said. That would imply they would arrive in 2021.