Sony has three different new FF prototypes in the works …

This makes sense to me . . . the business question is which segment of the market to target next, and one could make a business argument for each of these approaches.  I imagine from a technical perspective all of them are easily accomplished--it's just a matter of getting the details right and figuring out if the technical aspects can be met within the price range that makes it viable in the market.

My personal guess is that what will emerge is a "low priced" (relatively only to the A99) full frame camera, but that could simply be a reflection of my personal hopes.