depends entirely on how much they expect costs to drop. For instance, I would be very happy to provide you a 10 year warranty on 2tb of storage. Sure, it's going to fail and I'm going to have to replace it, but if I can get you to pay a price that would seem fair to replace the thing once or twice at today's prices, most likely when your device does fail, I'll be able to replace it with much cheaper parts.

(Of course, this ignores the format differences; if sata goes out of style, it could actually cost me more to source a sata part. Of course, judging from how long PATA lasted in a largely backwards compatible format, I /probably/ wouldn't have to worry about that too much in the next 10 years, but it'd be a source of worry. I'd be much more comfortable promising you 2tb of storage of some type with some minimum performance level, and not specifying interface, or selling you network-accessible storage for the next ten years.)