Bandai Namco have issued a report and they announced that Tekken 7 sold more than 3 million copies worldwide ever since its initial release.
Mr. Harada himself wrote on Twitter that the milestone was reached just after the anniversary was (properly) celebrated. The entire franchise sold more than 47 million copies since 1984, so that's another reason to celebrate.
The game is having regular updates all the time, so we have a good reason to keep playing!