The car won't stop working just because they do updating the software. At least in America they have to provide parts for at least 10 years. And eventually they won't be able to continue to yell copyright to prevent people from updating the software
There are people with John Deere tractors who claim they can no longer use said tractors because the tractor's owner won't pay for an authorized tech to come out and plug into the tractor. Because farmers have to be frugal. So maybe they can yell copyright.
On the other hand, things with engines can hurt people so you cannot allow unconstrained access to that port. Safety, IP and "who owns what" will make things more interesting as things emerge.
This is actually an interesting question when combined with OTA updates. Could (auto maker of your choice) theoretically supply all the parts you want but deny you from using them via software blocks? Or would that be illegal?
If the software is internet-facing (hint: it is) and contains unpatched vulnerabilities, it could easily be made to stop working by a drive-by (hah) script kiddie attack.
