Apsc is still going to be the sweet spot and most likely their volume leader. When and if they come out w/ their version of a apsc offering, I hope they do the same sort of thing Nikon has done w/ their dslr bodies to support dx/fx lenses ( if I remember correctly, someone at Fuji already said that current lenses will not handle ff).
In that article, they are --> not going to sell their sensors tech to anyone else and that have capability to do a full frame, but are not planning to do so now... Which tells me the product managers have asked the engineers and have at least gotten the high level idea of what it takes to make it happen.. The way the guy said it leads me to believe that they have not committed engineering teams to anything outside of a prototype design on paper yet. Only time will tell the real story.
For me, I am not interested in ff xp1 equiv. dof, dynamic range, and better iso.. Plus using ff lenses at their intended focal lenses while nice, I am already happy enough w/ what I have in apsc from the xp1 that I will probably stay w/ it or the xp1 next gen for now. I am not a dof separation type, the 1.4 is good enough for me and if I need portrait work, I can use a canon rf 50f1.2. Iso performance of current xp1 is more than what my current needs are. So the only thing would be better dynamic range, which a next gen xp1 could accomplish.
A ff x100s, actually may Interest me more as an eventual replacement for my x100 when it finally gives up the ghost.
Cheers
Gary