A teaser on the Pentax Japan website appears to suggest that the 645D will be showcased at the CP+ Camera & Photo Imaging Show, which begins in Yokohama on 11 March.
In 2008 Pentax appeared to have scrapped development of the 645D altogether.
But last year we revealed that Pentax had revived plans to launch the camera.
Only a mocked-up version of the 645D has been shown to journalists.
It has been paraded at numerous trade shows since it was first mooted at Tokyo’s Photo Imaging Expo show in March 2005.