I ordered my Pentax K20D (now sold but no fault on the part of the camera) from Amazon and they showed a delivery date well past everyone else.
B&H got it in, I cancelled my order with Amazon, paid $50 for overnight shipping and two days later, Amazon had it in stock. As a prime member, next day shipping is $3.99 so that hurt a little.
I do not know why they're conservative on their delivery estimates but they are HUGE and I expect them, worst case scenario, to have my D700 within a few days of the major camera vendors. If not, I'll pony up for the extra postage again, assuming I can find one somewhere.
Until then, I am "limping by" with my D300! FX/DX...here I come!