For the first time, as of today, Amazon’s website and ordering process is not guaranteeing November 15 shipment of newly pre-ordered Kindle Fire units.

As of Friday morning, Amazon’s Kindle Fire ordering page says “Expected to ship in 3 to 5 days” for the Fire tablet, which of course could still mean a November 15 shipment, but does not guarantee that ship date.

For a Kindle Fire that I ordered this morning with overnight 1-day shipping, the Order Confirmation provided by Amazon says “Delivery estimate: Nov. 16, 2011 – Nov. 18, 2011.”

Please note: If you pre-ordered a Kindle Fire before November 11, no worries, because Amazon has been very clear that it will ship by November 15.

So, what remains to be seen is whether this is a temporary hiccup in Amazon’s supply chain for the Kindle Fire, a hedge, a bit of stress marketing to accelerate pre-holiday orders, or — worst case here — some sort of sad repeat of the 2007 and 2008 holidays seasons when the vast majority of pre-holiday Kindle orders were not shipped until February or March.

Nobody knows exactly how many orders Amazon has received for the Kindle Fire in the six and a half weeks since it began accepting pre-orders on September 28, but we’d guess that it is very close to the point where Jeff Bezos could, in passing, casually drop the word “millions” without stretching the point. But what has changed in the last few days is that in a press release on Tuesday Amazon “announced that over 16,000 stores across the U.S. will be selling the new Kindle family starting November 15. Customers will be able to visit any Best Buy, Target, Walmart, Staples, Sam’s Club, RadioShack, Office Depot, as well as several other retailers, to experience and purchase the $79 Kindle, the $99 Kindle Touch, the $149 Kindle 3G and the $199 Kindle Fire.” Even with the most efficient possible just-in-time inventory management by those retailers, those distribution channels will require at least two million additional Kindle Fire units at or very near the November 15 release date.

We’ve been impressed with Amazon’s ability to stay ahead of heavy demand for all its Kindle models since March of 2009, so we’re not predicting doom and gloom here. But I will say that this morning’s slight hint of the possibility that the demand might edge ahead of supply has us going over our Kindle Fire orders again just to make sure that we’re in a strong position to deliver the tablets to all of our winners in our Kindle Nation weekly giveaway sweepstakes.