Unlikely to even arrive on mars, typically we need to make course adjustments en route and a car doesn't exactly have thrusters. Hence the comment in the tweet about being in deep space for a billion years or so.
I wonder how long the battery pack on the tesla will run the radio.
So actually, they'd for sure have to disable the heater on the battery, and I dunno, can the battery operate enough power to power the stereo when it's negative crazy low temp in space?
edit: Unless by Mars orbit, he means, a solar orbit similar to the orbit of Mars. Which actually probably is what he means. It's just the right blend of technically correct, but slightly misleading.
I guess in theory you could use aerocapture to avoid leaving if you aimed it just right, but without thrusters that would eventually mean hitting the planet.
The next mission might actually carry a Tesla rover to the surface. Then maybe a large battery-backed solar array so the rover doesn't need to worry about its energy budget anymore. The "silly" mission could even help Tesla/SpaceX gain important insights about how their batteries fare in space. Never underestimate Elon Musk, even when he seems to be having too much fun.