For one stop more shallow DOF? Or for the 1 stop improvement in noise when you look at your screen at 100%?
There's only a tiny percentage of photographers who are going to see any real world improvements with a 35mm sensor. The camera will be bigger (at least the size of an XPro1). The lenses will be bigger (Leica lenses don't have AF to worry about). A body will cost at least $2K (2.5K with a lens), so 90% of people will just bitch about the price. None of the superb existing lenses will be compatible. You may actually need a different lens mount. For 1 stop of DOF difference I don't see the point especially since you can paint a stop of blur in Lightroom.
IMHO. Fuji would be better making the focus of the existing system competetive with the EM5 and Sony just need to make a few lenses rather than yet another body.
I used to be a cheerleader for a Fuji X full frame.
But then I really put thought into it and realized the XPRO1 and XE1 IQ already competes well with full frame IQ. Instead of creating an entirely new system, I'd rather have Fuji put their focus on making their ASPC cameras even better.
Getting too many body types out there, without supporting lenses, doesn't help sales all that much. Look at the NEX line for instance, or Samsung. Lack of lens choices has limited the growth and acceptance of those systems to a greater or lesser extent.
For Fuji, starting a new line of full frame bodies and diverting their lens production into it as well reduces their ability to grow a reasonable lens lineup for both systems. From what I read it appears that they have done a good job at putting out only a few higher quality offerings lens-wise, while steadily evolving the system as interest builds.
One of the reasons micro four thirds has had the unlikely growth it has is because of the strong lens support. Thom Hogan calls this a "chicken and the egg problem". There's no use designing and manufacturing lenses if nobody buys enough bodies; but nobody will buy enough bodies unless the lens choices are there.
Now, if they do a fixed lens to compete with Sony for instance, that's a different deal entirely. Then you don't have to engineer a whole new system of lenses.
To me, the final problem with full frame compacts with interchangeable lenses is the size of the lenses. If you put leaf shutters in, put the lens very close to the sensor, and use just primes you can be very small and still be fast. Lili posted about that showing an old film compact Olympus with an f/2.8 lens. But if you do focal plane shutters and want fast wide-range zooms the lenses will be as big as DSLR's. This kind of makes "compact full frame" an oxymoron in that case, lol.
It wouldn't make sense for Fuji to develop a FF camera. My understanding was that the X sensor was developed to be as good as a FF sensor without the FF cost or relative size of larger cameras and lenses.
Defining the imaging circle of a new mount is one of those big decisions that lives for 20+ years. X-mount is APS-C. It would have been terribly short-sighted of Fuji to release the X-mount based bodies and lenses and just a couple of years later release full-frame. Just doesn't seem plausible.