Sadly, accidents are probably going to happen before infotainment gets decoupled from CAN bus. You don't just need a firewall, those need to be on physically separate networks.
Or are you thinking that just a bug in the infotainment system might cause it to shut off someone's brakes when you play a song which contains a null byte in the wrong place?
For a long time I've wondered what would prove to be Security-Pocalypse that finally convinces everybody that this is a real problem. This is not yet it. But if somebody takes one of these attacks and gets... "creative"... in those ways that aren't really that hard to come up with but I hate to actually spell out online (it's scary to think too hard about this... there's no possible way these vulns could be closed before a bad actor could... be very bad...)... that could become the moment the 21st century finally realized that secure code is no longer optional.
That will be one hell of a shakeup.