Spinning disks are hanging on to the very large end of the curve, where cost per GB really bites, but "smaller" drives (under 1 TB) are rapidly switching to SSD storage. I wouldn't count on that holding much longer, though. If it were straight replacement for incremental improvement the march would be slower, but the fact is that SSD storage has clear and significant improvements. This is true even when it uses SATA interfaces, which are clearly not optimized for SSD. Wait until PCI interfaces become mainstream.
I thought so too, but he works on those big tape arrays and swears there is enough error correction and redundancy to make them safe, besides being more cost efficient than spinning disks of data no one is looking at.