Nothing much to shift there, given the body and mount size. It should be possible though an adapter, but it isn't particularly desirable - the not exactly cheap XPan lenses will be rather underperforming on a APS size sensor. And I doubt Fuji will do a digital XPan one day when sensors of that size become reasonably affordable, as that probably never happens - outdated medium format sensors tend to become too expensive to compete with smaller formats and vanish rather than reappear in some lesser medium format camera.
It is more likely that we'll eventually see 16x35mm "wide format" cameras derived off FF and APS-C - the popularity of wide formats in cine production and convergence of still and video will certainly push that way. But such a thing would probably either have a FF compatible mount or its own lenses - there would be no point in using a mount for lenses with three times the coverage.