I remember when you joined, you had an A6400 back then. I guess you upgraded to the A7IV 2 yrs ago? Do you like it? What do you want to improve upon? More megapixels? Better video performance?
If you wait another 10-12 months, rumor has it that the A7V will be announced. Nobody knows yet what the specs will be, but the megapixel count is sure to be less than the A7RIV or A7RV.
Or you could get the A7RV now for more megapixels and a really cool rear screen.
I have an A7RV and it is a really great camera. If you have an A7IV, I would agree with @FowlersFreeTime. I would be waiting a few months to see if there is any news of an A7V.