There will probably still be a handful of '80s-'00s cars running in 2050+. There are some bulletproof Toyotas and Hondas out there.

You might have to replace the frame every few decades as it rusts, but that is possible with body-on-frame construction. They're also simple enough to be maintainable and repairable until their ECUs croak - maybe even then, with something like speeduino.

If you want, you can still pick up a cheap one from a dry, warm area and make your own car of Theseus. It's not cheaper than running a new car after the initial purchase price, of course.