For example, my laptop has a 250GB HDD and I have a few (read: too many) external hard drives that add up to about 10TB.
I would love to replace my laptop drive with a SSD and the external drives with one or two of these new 6TB drives.
SSDs are great, but that doesn't some people won't also need big HDDs.
How soon until Dell, HPs (etc) ship more desktops with SSDs than with mechanical drives? The average consumer doesn't understand the difference and doesn't want to pay extra (even though it's probably the best performance/$ upgrade possible).
On the flip side, I wouldn't be surprised if we saw significant adoption for servers that can live with the space limit (or that can design around it). Server-based applications are often I/O bound, established solutions are expensive, and the people responsible know and care.