Sony officially announces the a7CR and a7C II along with the FE 16-35mm f/2.8 GM II

[koenkooi]

And you get the wobbles when shooting video. I don't think IS is really as beneficial as IBIS is on the wide end. For example using the EF 16-35 rather then the RF IS lens, the wobbles appear to be almost non existent.

IBIS is causing the wobbles and when using EF lenses IBIS will run in a degraded mode, especially if the EF lens has IS. Try the RF16mm on an IBIS body and you’ll see
lots of wobble.