This month a major milestone was reached in the world of solid-state storage. For the first time, the capacity of an SSD was greater than that offered by a hard drive. The biggest hard drives on the market today are 10TB, but Samsung has achieved a 16TB SSD. According to Toshiba, that storage divide is going to grow massively over the next 5 years.

The 16TB SSD is a significant achievement not only because of the huge storage capacity, but because the SSD retained its 2.5-inch form factor. Anything above 2TB in a hard drive and you’re looking at a 3.5-inch drive. And the size of the storage component increasingly matters when you consider consumers continue to move away from desktop PCs and over to Ultrabooks, tablets, and smartphones. The same is true in data centers where space is always at a premium.

So how big is the gap between HDD and SSD going to get in the coming years?

Speaking at SEMI Members Day Tokyo on August 20, Toshiba Semiconductor & Storage Company’s chief engineer Nobuo Hayasaka, predicts that hard drive capacities will reach at least 20TB by 2020. However, it’s possible they will double that to 40TB while retaining a 3.5-inch form factor. For SSDs, he paints a very different picture. Next year we can expect 32TB drives. By 2017 that will increase to 64TB, and in 2018 we’ll see 128TB drives hit the market. Beyond 2018 SSD capacity is expected to accelerate, meaning it won’t take a full year to get to 256TB and so on.

We all knew that SSDs would eventually replace hard drives as the storage format of choice, but it always seemed 5 years away to me. However, it’s happening now, and by 2018 the transition will likely be complete. Consumers will be buying in a market that mirrors how memory cards are now sold–a new, larger card hits the market and smaller card pricing falls off a cliff. Expect the same for SSDs, only when we reach 128TB drives it will be 1-5TB SSD pricing that hits rock bottom, and I welcome that day.