while it is clear, that it is very difficult to completely retrofit current Teslas with new features or Elon would catch opportunity to offer upgrade, there are few things which could be done 1. install new 8 meters ultrasound sensors in place of current sensors 2. new radar in place of old radar 3. additional cameras (installed in rear view mirrors?) 4. new computer. so what can be achieved with this upgrade? that won't give all capabilities of self driving, but might be a huge step above current autopilot abilities. while it is not a priority to offer such an upgrade - still to offer such option will be a great gift from Tesla for those who want better autopilot and given that anyway regulatory approval of complete autonomy is years away that upgrade could allow current fleet not to feel obsolete for owners.