I have been told by trusted sources, that the new Fujfilm GFX100 will be “about as big” as the Fujifilm GFX50S.
And remember, the new Fujifilm GFX100 features IBIS!
It’s astonishing how much Fujiflm has downsized the IBIS unit in such a short time, considering that the one on the Fujiflm GFX100 clearly does not fit in the GFX50S or GFX50R.
Oh, and if you wonder what that “Xg” camera is next to the Fujifilm GFX50S, that’s one of the Fujiflm GFX mockups that Fujifilm has shown to DPReview back in 2019 here.
I have no idea who the new Fujifilm GFX100 will look like, but certainly it would not hurt if it would like that mockup.