I wouldn't be so sure about value retention. The EV space is evolving quickly and there are huge advances between car generations. The rapid tech advancement will probably depreciate the Porsche Taycan just as fast or faster than the Model S.
I could almost bet on that. Porsche is one of the most desired brands in the world, and thus far has always maintained its premium. Also, this will be their first EV, so has a chance of becoming some sort of collectors' item. The real world spy photos suggest that it looks a Panamera with an RC engine, though. A huge disappointment imo. Probably worth even 'what was promised and what will be delivered' meme.