At least one person stated that the sensor would be different based on images posted on other websites (such as 2:1 pano images on Ming Thein's blog), but a digital X-Pan has been ruled out by Nick. Ming also said in the comments of his blog that no pictures on his site were posted from the new camera (he's also under strict NDA). Most of the stuff Ming posts lately I believe is from the H5D-50c and CFV-50c (and some with the H6D-50c).
The current Sony 33x44 50mp is at least 2.5 years old (based on IQ250, H5D-50C, 645Z release times) and I'm sure production costs have come down since it was first released and implemented. It still produces outstanding images, so if Hasselblad wants to keep costs of the new camera they release tomorrow down and keep it MF, it would make the most sense to simply use that chip. Hasselblad also has existing experience with implementing the existing chip from the H5D-50c, H6D-50c, and CFV-50c, so using this chip would also allow them to free up resources to focus on the camera itself and how the new camera uses and interaces with the chip. If people desire other formats (square, pano, etc), it would make a lot more sense for Hasselblad to do this in software rather than design a new chip as others have stated. Masking via software also allows for flexibility with multiple formats/aspect ratios. For framing, again should be straightforward to mask a crop from output of the sensor with software.
If the new camera is indeed a mirrorless MF, I really really hope Hasselblad keeps it simple. I really enjoy the simplicity of my H4D-40...and even the Nikons I used for years. In comparison, most mirrorless cameras frustrate me to no end and tend to be needlessly complicated, despite their size and image quality. I have an A7R and an X-T1, and also have experience with Olympus. The menu systems of the Sony and Fuji are pretty awful. With the Fuji, almost every time I pull it out of the bag a setting gets changed and it often takes a trip to the manual to figure out how to change it back. I couldn't even set up a friends Olympus out of the box without consulting the manual. I'd love to see IBIS and pixel shifting (like in Olympus ___), but other than that I hope they keep the shooting experience (menus, button layout, etc) more similar to the H-system (or Leica S/traditional MF) than current 35mm mirrorless. I do wonder if they can put True Focus in the new camera...that's a nice feature on Hasselblads that helps distinguish them from the competition. In any event, I'm really looking forward to the announcement tomorrow morning.