LensRentals did run a short test on Sony 90/2.8G Macro, and it was amazingly good. Now DxO-mark has tested the 90/2.8. This gave me the opportunity to compare it to the probably best lens in that range, the Zeiss Otus 85/1.4.
The image below shows both lenses at f/4 which is probably best aperture for both.
Now, stopping the Otus down to f/5.6 essentially makes the curves overlap, as the Otus is a bit limited by diffraction. The Sony is still at f/4, so it is less limited by diffraction.
This says that the Otus is the better lens, but the Sony 90/2.8G is pretty close at optimal apertures.
For me it seems that the Sony 90/2.8G may be the best 85-90 mm option if f/1.4 - f/1.8 is not needed. I guess that I cancel my order for the Batis and buy the Sony 90/2.8G macro instead.