Mamiya hopes to ship a 22-megapixel camera sometime in the future. Their press release vaguely promises, "Mamiya is committed to develop these new models and desires to bring them as soon as possible to you!"
This is not your typical consumer digital camera nor even 35mm-equivalent DSLR [digital single lens reflex]. Mamiya makes 645 cameras, which are used by professionals. In the days of film, these cameras use oversized film to create large negatives (6cm x 4.5cm -- hence the name) for very high quality images.
To create the equivalent quality in a digital camera requires a very large sensor -- hence the announcment of 22 megapixels. Such a sensor does not yet exist; I think the largest is about 16 megapixels today. Thus, I think the press release is a positioning statement, rather than an announcement.
The sparse Web site provides few details, other than their cheapest camera starting at US$7,000.
I am wrong. There is a 22 megapixel sensor, and it comes from DALSA of The Netherlands. Their sensor allows photographs with a resolution of 4008 x 5344 pixels.