Several manufacturers are now offering 14TB hard drives, with each in a race to beat the other with more space and power.
Clearly, hard drives leave SSDs standing with regards to huge data storage and cost to acquire.

The use for huge hard drives must be limited, with one of the top applications being HD video.

The other problem is, of course, you'd need at least two of those drives for redundancy and security of data.
It also occurs to me that the energy usage would be significant if these drives are deployed in significant numbers, but, fewer high capacity drives might save energy from having lots more smaller capacity drives.

I don't have HD video to record, so I doubt i'd ever fill up a 14TB drive before it failed, so i'll stick with the smaller drives in the NAS.

As for reliability, tempting fate here, over the years i've had relatively few failures, although that might be related to the fact that i've upgraded many drives to higher capacity, certainly before a failure has occurred.

For general use, SSDs seem the way forward, if only the cost could come down a little faster.