I think it will be two phases : the first one is the reconnection to the new server as mentions the title of the email "Migration du système Porsche Connect à venir." the second could be an hypothetical future OTA-update after the car will be connected to the new platform ...
It's clearly...
I don't think so because in the email it's stated to first find a place where the car is able to connect. That means if it is an OTA-update, it wouldn't have been updated by lack of connection (so why reconnect then ?).