The Hitachi Deskstar 7K4000 4 TB is turning one year soon, and since then there have been many interesting events in the harddisk market. Still in memory and felt in the prices is the Thai flood from last autumn; although the prices are finally starting to move back to pre-flood. Then the consolidation of Hitachi into Western Digital, and Samsung into Seagate, leaving only two major HDD manufactures standing.
Since then, there haven't been to much interesting news, but maybe there are changes on the horizon. WD recently released a new line "WD Red", targeting the NAS market specifically. See storagereview.com's review for details. What's notable is not the line itself, but its internal composition: It's a 3 TB drive, but using 3 x 1 TB platters, whereas the Green line, at least initially had 4 x 750 GB platters. I am assuming that is still the case.
Four platters is the typical configuration for most high capacity, non-enterprise drives. It is possible to push in five platters, which Seagate has done previously, but four seems to be a good trade-off between reliability and size. As far as I'm aware, WD has not ventured into five platter designs before.
However, now that they have a line using 1 TB platters, why not take the next logical step and offer a 4 TB Green drive? And if Seagate is willing to do a five platter drive again, why not make a 5 TB drive? What is stopping both from taking the next step? Possibly, they are still licking their wounds after the flood? Maybe milking the market for the demand for current capacity drives before moving on? Either way, if we don't see new 4 and 5 TB headlines by the end of the year, something is really off on the HDD front.