.......but which images can be made with GFX which can't be made with a Z7.....where there will be a real objective (or subjective) difference that matters?
You probably need to go into pixel level to see a real difference (noise, details).
Both images can be printed without problems at A2 or A1 poster size. Viewed on a monitor I don't think there is a visible difference unless it is a cropped detail at pixel level.
And maybe the fine Z-lenses can't be matched by anything for the GFX.
Agree! It is always a risk to say "what we have now is enough", but given how images are presented and consumed, I think we are in a good position now to make that statement for a while.
And I think that the future is not going to be larger camera systems. The history of photographic technology has always been in the direction of making camera systems as small as acceptable. For this reason, MF is a dead end. It will be a niche, and niches do not get the investment required to keep up as technology progresses.