New Tesla needs new cars sold with the Self-Driving upgrade.
It's those cars that will be used by Tesla to help do the "extensive software validation" needed before they can prove it's safe for the car to drive itself. Until then, the drivers with the Self-Driving hardware will be "driving instructors" for Tesla - teaching the software how to drive safely. Evidently Tesla will be logging the drivers actions and then compare that to what the software detected and would have done - and when there's a discrepancy, Tesla can continue to make improvements to the software until the software is driving at least as well as the human driver.