This morning, the store opened with delivery estimates of December 30th with some variants quoting a January timeframe. Now, it appears the initial allocation has sold out as Apple’s website now reports February shipment for all models.
Apple released the new Mac Pro this morning, six months after originally announcing the product, so it is unclear whether the lack of availability is due to pent-up demand or issues with production. The new Mac Pro is the first Mac to be assembled in the USA, so production issues could be at fault. New processes and manufacturing flows tend to result in lower-than-usual yields.
For avid buyers, it may be worth looking elsewhere in the meantime. Authorised Apple resellers may still have stock of the machine. As an added boon, shopping around at other outlets can also shave some of the cost off the Mac Pro’s hefty price tag.