What lots of assumptions? that's a single inevitability that a self-driving car manufacturer, Tesla or otherwise, will go out of business, rendering the car offline only (the point made in the article) or worse, like the case with Android phones, you'll have plenty of vulnerable cars on the street and some community updates (like the work of LineageOS for instance).

It's the same point made in this computerphile video[1].

[1]: https://www.youtube.com/watch?v=PLiE0Nr8VOE