The sales reports on tablets address a drop in actual sales, not in sales rate.
Old tablets simply aren't being replaced as they break and the new models aren't compelling many existing users to upgrade. The installed base is actually declining.
In parallel to this, convertibles have become lighter, thinner, with longer battery lives *and* lower prices. Not many tablets can match the utility of something like this:
http://www.amazon.com/ASUS-Transform...ertible+tablet
Much less at $299 including the Keyboard.
Which leads to stories like this from an Apple Beat writer:
http://ct.zdnet.com/clicks?t=1775508...rand=ZDNET&s=5