The latest leaks suggest a global shutter, if so Nikon is really flexing its muscle while flipping off the competition when they pass them in sales as this will be a real next level gamechanger for cameras.
So no mechanical shutter limitations, no rolling shutter, no viewfinder blackouts and insane DX framerates as the center part of the sensor can be read independently from the rest of the full frame sensor. Processing and write speeds become the next bottleneck in the chain but with the current NVMe cards this should not be a real issue.