Seagate announced yesterday version 11 of their Barracuda hard drive range, to be released next month (August 2008) with a maximum capacity of 1.5TB. The news link has all the speeds and feeds if you're interested in how they have achieved this remarkable milestone.
I've trawled the 'net to plot the release of previous versions of the drive and their capacities at the time. Here's a graph of the releases I could find, going back to 2002. Trending the growth (totally un-scientifically of course), then we can expect to see 2TB drives by December 2008, 3TB drives by November 2009 and 4TB drives by June 2010. This may be a little optimistic as the trending is skewed slightly by the recent advances perpendicular recording has brought to capacity growth, but maybe not, as my recent post on Hitachi 5TB drives shows.
Unfortunately, sustained transfer rates for these drives have remained around the 100MB/s mark, so offloading a complete drive sequentially takes around 250 hours, by my calculations. I'd love to know how long a RAID rebuild would take (Seagate if you fancy loaning me some drives, I'll find out for you!).
As previously discussed, the increased capacities are good as they increase the GB/Watt and GB/cm3 density but we're going to be increasingly challenged by how we get data on and off them - especially when the drives fail.