The Porsche Taycan already exists and goes on sale at the end of the year. It's designed around an 800 volt architecture that can make use of 350 kW chargers. Porsche is also testing 450 kW chargers for the future:
I know specs are sexy but, you're missing one important detail here. Battery Longevity.
Tesla did not initially do this because they wanted the batteries on their customer's cars to last for a long time. Now that they have the data, they bumped it to 250kW along with the on-route battery warmup.
So far, I have not heard a single detail on how the Porsche Taycan deals with making sure the battery life is being preserved. This could have financial and ecological cost if not handled properly.
The same as it's done in every EV. The individual battery cells are charged in parallel to achieve the high rate of charge and the battery pack temperature is managed to ensure optimal battery performance:
Porsche's been making a particular point of the Taycan's temperature management. The goal is to be able to drive it like a sports car without overheating it. They talk about the Taycan offering "reproducible performance".
Teslas have a history of overheating when you try to drive them like sports cars:
https://www.cnet.com/roadshow/news/porsche-bmw-dc-fast-charg...
Volkswagen has already announced three cars based on their 800 volt platform to be released across the next three years:
1. Porsche Taycan in sedan and wagon variants at the end of this year: https://www.popularmechanics.com/cars/hybrid-electric/a21239...
2. Audi e-tron GT at the end of 2020: https://www.youtube.com/watch?v=uvNw15W_EK8
3. Porsche Macan probably at the end of 2021: https://www.cnet.com/roadshow/news/porsche-macan-electric-on...
And I'm sure there'll be other 800 volt cars from Volkswagen and other manufacturers in the future.