I'd definitely like to think that all of that stuff would be air-gapped, hard-wired and baked into the silicon (and E2E-encrypted, with a Trusted Computing mode

I'd definitely like to think that all of that stuff would be air-gapped, hard-wired and baked into the silicon (and E2E-encrypted, with a Trusted Computing model and auditable supply-chains), but I do worry that people are going to cut corners, fudge things when they're approaching deadlines, and not take into account an appropriate threat model when they're designing this mass-market consumer automotive stuff. The Chrysler hack in 2015 managed to get some fairly low-level remote access to things like the braking system. I'm also considering the possibility that governments might backdoor their own manufacturers with their knowledge in order to gain exploits to systems overseas or to carry out the odd covert assassination.