Today was the last day you could use SuperSaver shipping and be reasonably certain you could get delivery by Christmas. This evening, Amazon announced that you will now get free 2-day shipping (in the US) on the Kindle (Global/International), so you can guarantee getting the package, even if ordered as late as December 22. Of course, there is always the possibility that they'll run out of stock on these as well (after all, they are now practically the only eInk device left in stock, as well as the most popular one with buyers and readers). If you were looking forward to a Kindle DX in your stocking (and what a large stocking that must be!), you are out of luck - shipping estimates are currently 4 to 6 weeks out (then again, if it's a DX you want, you might want to reserve your place in line, as waiting a month may mean even longer delays (then again, a month from now, they may have their supply lines caught up and orders may start shipping right away again -- they definitely have that more under control this year than in the past and are handing holiday orders better than their top two competitors).
If you were considering a refurbished Kindle, most of your $40 savings may be eaten up in shipping costs to get delivery in time for the holidays. You are also out of luck on a refurbished Original Kindle or Kindle DX, for now -- if refurbs of either one show up in the store, they disappear almost instantly and both are currently out of stock.