Yes Porsche has started with this, they have ~800 V batteries, as you said batteries themselves are the practical limit at the moment but both larger batteries

Yes Porsche has started with this, they have ~800 V batteries, as you said batteries themselves are the practical limit at the moment but both larger batteries (as with trucks) and new battery technology can help to lift that limit. There are enough engineering challenges at 1000 A I don't think we will see higher currents than that for a while!