Unfortunately when we have reliable, safe, self-driving cars, the loudest complainers will be truck drivers who now have to find new careers. I hope I don't sound too mean to hope their concerns are ignored.
It doesn't really matter what they're shipping - a truckload of TVs is nice, but even a truckload of sh*t is valuable enough to make it worthwhile.
In the long term, though, you're most likely right; truck drivers will have to find new careers. However, said legislation combined with what I believe will be slow adoption due to high cost should give truck drivers a decade or two to migrate to other jobs.