Under SKU code HDS5C4040ALE630 and probably part of the Deskstar 5K series, the 4TB drive has yet to be announced by Hitachi but it can be found on sale in Japan, priced at 26,800 yen (~ US $ 345 / 259 Euro).
Hitachi's 4 TB hard drive has 32 MB of buffer memory, a SATA 6.0 Gbps interface and makes use of the CoolSpin technology, which means its four platters operate at around 5900 RPM.