My order was delayed until the 17th as well, here's what I have been told by different customer service agents...
Microsoft is aware of the shortage and is working with Dell to fulfill the orders. It is likely they will be replacing the Brown Zune with either a Black or White Zune and a letter of appology will be included with your Zune.
They insisted that I shouldn't be concerned or cancel my order because they will fill it, I had explained that I read on the net that quite a few people decided to cancel their orders as soon as they saw it was back ordered.
Lastly, the woman mentioned that my delivery date had been moved to Dec. 11th. It did not say that on the website, but she assured me this was the case.
I will update as soon as I have that little fella in my hands...
HANG IN THERE AND CROSS YOUR FINGERS!