For those that submitted their preorders early, good news!
B&H is now shipping the Sigma 50mm f/1.4 DG HSM Art Lens for Canon (review). From what I've been told, they haven't received a significant supply yet (low quantity shipment) but they are now shipping out what has hit their shelves.
B&H still lists the Sigm 50mm f/1.4 Art lens for Canon's status as being "Pre order. Released in limited qty."
B&H has the Sigma 50mm f/1.4 DG HSM Art lens available for preorder.