Pentax 645D is revealing itself slowly
The Pentax 645D teaser is actually slowly displaying more details of the camera - now we can see the shutter release:
The teaser started on February 9th. Six days later the progress bar is aprox, 1/5 of the way to the end. That means the official announcement should somewhere around March 9th-10th, 2010. There were some rumors that the 645D will be unveiled at the CP+ Camera and Imaging Show in Japan (March 11th-14th, 2010).
Here is a prototypes picture of Pentax 645D (courtesy of Pentax):
Pentax 645D back view (source: Pentax Japan)