One of the comment
"I'm testing one of the prototypes: 3 different configurations exist. The one I currently have has the same sensor as the D600/A99 ... There is another model which has the same sensor as the D4 (much more expensive as a final product)... so far I'm loving it. Too bad I have to keep it taped up whenever I have it outside though.
ISO goes to 102,400 and is clean up to 12,800 (I mean, perfectly clean) Burst is still 7fps. Body is heavier than my K-5 IIs but is the same size (just heavier because of the larger mirror/prism. SR works like a dream, and the new features they are trying to implement... wow! (Bugs still have to be worked out with some of them... most of them...)"