Apparently stated by Andrew House via this PS Awards stream going on right now, the PS4 has sold through (meaning sold to customers) 2.1 million units since its launch worldwide.
It's been officially posted by the PS Blog now:
In what is shaping up to be a historic year for gamers, I’m delighted to share an important new milestone with you. PS4’s North American debut on November 15th was PlayStation’s largest ever, with more than one million gamers picking up a PS4 in just 24 hours. Now, with PS4’s global launch expanding to a total of 32 countries worldwide, including Europe and Latin America, I’m proud to announce that more than 2.1 million PS4s have been sold.