I understand the question is about lenses, but personally I would not buy an a7rIV now.
It was released exactly 2 years ago and many a Sony shooter, including Thom Hogan, find the mkIII to be the better camera.
I used to own a mkIV and was never in love with its image quality, nor with its color rendering.
Sony has improved color filtering significantly since the a7sIII and a1. I would expect the a7rV to benefit from this. No idea when I would become available, but I would expect late 2021 early 2022.
Just my 2 cent.
Cheers,
Bernard