The article says they are pushing for 20TB drives by 2020. That means they are saying 7 years from now we will be using the same technology but the drives will be larger. They are clearly talking about non-SSDs in the article.
SSDs are ok for now but they are still not even close to being reasonably priced. A 1TB SSD is like $650, completely gouged.
I have a 300gb drive and it still has 180gb free. I have a ton of stuff backed up too and quite a few large apps/games.
With more things being "stored on the cloud" it surprises me that HD manufacturers go after space instead of speed/reliability.