To answer AT's original question:

when we will see 1TB hard drives now that Seagate have started producing drives using perpendicular storage
My initial answer is "What is the Time Now!"....

2000s

* 2002 - 137 GB addressing space barrier broken
* 2003 - Serial ATA introduced
* 2005 - First 500 GB hard drive shipping (Hitachi GST)
* 2005 - Serial ATA 3G standardized
* 2005 - Seagate introduces Tunnel MagnetoResistive Read Sensor (TMR) and Thermal Spacing Control
* 2005 - Introduction of faster SAS (Serial Attached SCSI)
* 2005 - Perpendicular recording introduced in consumer HDDs (Toshiba)
* 2006 - First 750 GB hard drive (Seagate)
* 2006 - First 200 GB 2.5" Hard Drive utilizing Perpendicular recording (Toshiba)
* 2006 - Seagate announces research into nanotube-lubricated HDDs with capacities of several terabits per square inch, making possible a 7.5 Terabyte 3.5" HDD[6]
from http://en.wikipedia.org/wiki/Hard_disk
HAve heard of HDDs in the market place of the 750 to 800Gb range.. so the 1x10^12 byte drive wont be far away.. pick a release date.. but a true binary rated 1Tb drive will be a bit beyond that

As for:
I don't think that most mere mortals actually have a need for terrabyte scale storage
wasnt it mr William Gates III who said something abot 640kb of ram?

Seriously.. average home joes who have had 80gb hdds in their pc's and useing there pc for the legit home office use, accounts, wp, basic spreadsheets, and some Internet are lucky to have used more than 25% total drive space..

Home users normaly expect speed.. and think that hard drive size is related to speed.. so while the numbers keep growing many people will buy the largest thinking it will give them better performance.. But I agree that solidstate will be the best.. I would rather a 20GB lightning fast solidstate HDD, and near instant cold boot speed for my work and home use than a 500Gb mechanical hdd..

now that said.. people with media center PC's will expect and happilly use what ever large size hdd their given..

as for me..man the sooner I get another 1TB of storage the better..