That is a question many would like answered, and soon. However, battery life would likely be a major LIMFAC if you're talking about a camera without the "grip."Will there be a Z850?
Now that I've thought about that, I've put a deposit down on a Z9 and an adapter. I can't explain to anyone, including me, why I did so. It goes against every rule I had for obtaining electronic items; the first of which was to never pay to be a product tester.
One thing I'm fairly confident in is that there won't be any issues with oil from the shutter mechanism spoiling the sensor.