As noted by a number of MacRumors forum members and Twitter users, Apple has begun preparing a number of stock Mac Pro configurations for delivery starting on December 30. In addition, many other users are seeing their credit cards charged and order statuses changed to "Preparing for Shipment". The new status indicates that orders cannot be canceled or changed and are in the final stage before the new Mac Pros are handed off to delivery companies.
It appears that the first shipments of the Mac Pros are all stock configurations, as it has thus far been unclear if custom configurations have been shipping out to users. Since online ordering has been available, the shipping estimates have slipped into February 2014, with demand outstripping supply.
Article Link: Apple Begins Preparing First Mac Pro Orders for December 30 Delivery