From the Department Of the Bleeding Obvious
If people are not buying HDDs but instead relying on "The Cloud" for storage, then it stands to reason that "The Cloud" is going to have to buy just as many terabytes' worth of HDDs instead.
Actually, make that "at least just as many", since users probably are more likely just to delete files to free a bit of space on their own devices, which they would leave there if the storage space was officially Some Other Fool's Problem.