It's not just the 3G model that is out of stock; I think Amazon has quietly discontinued all Kindle Keyboard models. Both the 3G and the Wifi models of the Kindle Keyboard are out of stock at Amazon.com, Best Buy, Radio Shack, and Staples. But that's not all; I can't find any Kindle Keyboard models in stock on Amazon.co.uk, Amazon.de, or Amazon.fr.
I'm still waiting for official confirmation from Amazon but the current stock situation presents a pretty clear picture. This ereader has been discontinued, or at the very least it looks like Amazon has stopped making them.
Update: I have an early response from one reader who was told by Kindle CS that the Kindle Keyboard has been discontinued:
I understand your concern that you love the Kindle Keyboard device and I'm sorry to inform you that our company does not manufacture the old Kindle devices due to the in demand of the newer version of Kindle devices. I'm so sorry for the disappointment caused.
Amazon initially launched the Kindle Keyboard in August 2010 as a replacement for the K2, which was launched in early 2009. The KK followed the the same design as its predecessors, and it had a 6" E-ink screen, 4GB of storage, speakers, and a keyboard.
Amazon launched more Kindle models in 2011 and again in 2012, but for some reason known only to Amazon they kept the KK around. Amazon even pushed out updates for this ereader which gave it support for the latest features of KF8. Many owners appreciated that Amazon kept it around, because after Amazon replaced the Kindle Touch with the Kindle Paperwhite, the KK was the only Kindle model that was equipped with text to speech.
I thought Amazon had kept the KK around because it filled a different product niche than the basic Kindle and the KT/KPW, and now that the KK is gone I have to wonder what will replace it.
While it is possible that Amazon killed off the KK simply because it wasn't selling well anymore, there is also a chance that Amazon is going to replace this ereader with an updated model. We could soon see a KK with a 6" HD E-ink screen, or possibly even the 6.8" screen that is currently used by the Kobo Aura HD.
On the other hand, I checked the FCC and there were no new filings that might possibly belong to Amazon. So perhaps the KK was simply discontinued.
I am waiting to hear from Amazon, and I plan to update this post if I do.