Maybe I'm being myopic as far as the definition of firmware. I've never heard of a firmware update for a car, but if it's not happening already, it'll probably be part of the regularly scheduled maintenance in the future.
Essentially nothing like that is used anymore. Almost every programmable part is reprogrammable in-system unless someone takes extraordinary measures to prevent it from happening. That means that there is no longer any real distinction between "firmware" and "software," and there is no such thing as "read-only software," as you put it earlier. There is only "software" and "locked software."
This thread is all about who should own the keys to the lock.