As a passionate Compute Storage Guy (well somebody has to be), I've been monitoring >5TB Hard Disks for absolutely ages.
They have arrived, buT, bUT and BUT.
Mach 2014: I was salivating as drives were already announced, just not quite shipping
May 2014: Well it was my Birthday (excuse #1) , but mostly I was fed-up of waiting and voted for 4TB drives
June/July 2014: They arrived. BUT BUT BUT
How flippin expensive?
Hitachi 7K4000 == 190 CHF
Seagate ST6000NM0024 == 490 CHF
Hitachi Deskstar H3IKNAS40003272SE = 122 GBP
Seagate ST6000NM0024 == 411 GBP
So, in summary. To all of you who have waited for cost effective 6TB drives, think again. 4TB should be your choice for the immediate future.
And, given the stability of that disk drive manufacturing shrine (Thailand), I would stock up sooner rather than later.