I can't speak to GFX glass, but as far as QC on the Fuji XF glass, it's been great for me. I have yet to find a lens that needed anything adjusted. Fuji's XF glass has a great reputation also. I have to assume that Fuji will continue making the lenses for the GFX, and it's a bet I would take, (the lenses will be excellent). Plus they have a lot of heritage from making lenses for Hasselblad.
And has been mentioned already, Fuji's advancement via Firmware, giving new features to older cameras, is by far the best from any company I have seen. Safe to assume again this will move forward on the GFX also.
Only issue is the sensor and Sony, and hopefully Fuji and Sony have a good deal worked out for supply.
Paul C