If it helps, I pay reasonably close attention to Fuji rumors because I'm deep in the ecosystem, and at present there appears to be no indication that an XT-6 is coming any time soon. They just released the GFX100RF and XE-5, plus there are rumors of an X-T30 III soon, and with all that in the pipeline I doubt they are also finishing up an XT-6. The -4 and -5 are still great cameras, I would just go for whichever of those you think is a better deal.