It was only a few days ago I mentioned Western Digital's new 6 TB disks. It seems Seagate got nervous, and are now claiming to "ship" 8 TB disks. However, it is a misleading headline at best: The drives in question are not on sale anywhere, and only special "pre-production prototypes" have been given to few select partners. Furthermore, the initial batches will be aimed at enterprise customers who can afford them. As an early-adopter strategy, that makes sense, but it means you will not get your hands on one any time soon. So, the prediction from a few days ago holds: 8.4 TB is already within reach, with 7 platters * 1.2 TB, but needs special technology like helium filled drives. We will probably not have 8 TB drives before 2015.
The bit-tech article is also very light on technical detail, presumably because Seagate holds their cards close. There is no mentioned on how they have gotten to 8 TB, only that 10 TB might also be within reach soon. The later would be very interesting, since even with 7 platters it means an increase in areal density to 1.4 TB per platter. Or if we assume 5 platters, an impressive 2 TB. That will probably not reach the market before end of 2015, possibly 2016.