I have put a little thought into this and trying to be as pragmatic as I can. I would truly like to see a FF camera from Fuji. But the reasons are not all that technical. Where I see Fuji using FF is only in the X100 line (at first) I feel that that line was well positioned to be a major alternative to Leica and its success shows they were right. The economics of a slight redesign of the body to accommodate size and development of "one" awesome lens seem to justify this move. The idea of a MF is just to niche for any significant profits. There is very little chance of pulling sales from other lines as well. There is a builtin user base that will upgrade and sidelined base that will adopt. Lastly, I feel users know the X100 as the test platform for the other lines and this move will be easily accepted. It all points to low risk, good profit and steady progression.
For those that look to how well the XTrans performs, you are right. And as ZA has noted there is very little of a jump from the current platform to FF. That said, in consumer products it is very rare that a company will make a quantum leap in technology. Look at Autos, clothing or Cell Phones and 100s of other segments, they all move in small steps.
Save the organic sensor for the X-Pro line and you will get more folks buying two cameras Not that everyone wants to shell out more $$$ but this is about Fuji as a business.