Yes, that day will come. However the outcome from that event won't be what you may think.
If we take 9/11 as a template of idiotic reactions to terrorist events, here will be the likely outcome:
1. The true perp, the decision makers(marketing management, etc; not coders) who enable cars to be the toys of hackers, will avoid any blame. They will be swiftly whisked off to team building sessions in Aspen, Cancun or Jackson Hole, where they will be presented with awards for their forward thinking and accommodation to user comfort and convenience.
2. The proxy perp, who actually drives the cars to the left, will be swiftly arrested, convicted and jailed, and become a scapegoat for those receiving awards for forward thinking and accommodation to user comfort and convenience.
3. Users and "car owners" will be the real losers here. Even more restrictive rules and engineering will be placed on modern cars, whereby the bank you got your car loan through will be able to deduct funds directly from your bank account if any number of intellectual property violations are committed such as humming the Star Spangled Banner on the way to a 4th of July picnic. Any modifications, however subtle(including but not limited to "support our troops bumper stickers"), to the vehicle will be met with a swift kick in the ass from your local dealer, and more funds being deducted from your account. More "security" measures will be implemented, as per a Congressional Oversight Committee, that will, in essence, hogtie users/drivers even more and allow even more vectors for attack by hackers in Bulgaria, Boston and Beijing, but you already knew all that...