You'd Figure the prism would be the easiest things to make happen.
From the looks of the Sinar back it looks like it will be difficult to have a 90 degree prism because of the length.
Will they maye a 45 degree prism?
Was it finally released that the back is rotatable or do you have to remove it and put it back on to switch from horizontal to vertical.
The camera just seems like a non-starter to me for use outside a studio environment until there is a rotatable back so that you can easily switch into vertical mode. I cannot imagine removing the back in anything like a harsh, external environment every time I want to shoot a vertical composition. With an H series body and an L bracket, switching to a vertical composition is quick with no risk of contamination of the sensor with dust, dirt, sand, etc.
Too bad. The Rollei guys are surely capable of developing a very well engineered 645 camera body that could surpass the H series in many ways, with great lenses to boot. It just seems that the marketing people running these companies don't talk with the professional photographers out there to find out what they really want. Maybe I am wrong. Perhaps there is a large market out there of people who want a camera like the Hy6 that uses a 645 sensor with a finder configured for a 6x6 film back and that requires you to remove the back to shoot verticals. We will see.