I've thought about this a bit.
After seeing the announcement of the canon and Nikon FF mirrorless cameras and their respective lenses, I don't think Fuji will be tempted to the FF category, and neither would I want them to.
The Xtrans aps-c Fuji's are so close in IQ to the FF cameras, yet have smaller, more tactile, sweeter lenses thanks to the slightly smaller format. They absolutely nailed the size to quality ratio.
Take a look at these lens size comparisons:
Fast 35mm equivalent lenses -
http://j.mp/2NYw6Kq
Fast 85mm lenses -
http://j.mp/2wTwoLV
It seems that the mirrorless bodies from sony/canon/Nikon are employing even larger lens designs than their mirrored equivalents.