Don't know how many there are, but CCS charging networks have been installing 350 kW chargers for over a year now so I put the figure at "many":

https://fastned.nl/en/blog/post/fastned-onthult-nieuwe-gener...

All cars can use the 350 kW chargers to charge at the car's maximum charge rate (whatever that is for the particular car). The Porsche Taycan has an 800 volt battery system and can make full use of a 350 kW charger. The Taycan will be released at the end of this year. Here are Porsche's specs for the Taycan:

https://newsroom.porsche.com/en/products/porsche-taycan-miss...