There's a very simple update mechanism for any car (or anything that doesn't get put in space or dropped to the bottom of the ocean, really). Recalls. They're

There's a very simple update mechanism for any car (or anything that doesn't get put in space or dropped to the bottom of the ocean, really). Recalls. They're expensive, annoying, etc. But they're safe (or safer, at least), and if you screw up badly enough that a safety-critical system needs an update, they're necessary. I don't think anyone is arguing that the infotainment system should be disconnected from the world, but the core driving systems (steering, brakes, transmission, etc) should be air-gapped and inaccessible without physical access to the interior of the car. Also, that access could (and maybe should) be disabled when the car's engine is running, preventing an attacker from plugging in a wireless device and then subverting the system with the car in motion.