Of course that was said tongue in cheek. Orbits degrade over time and are corrected with microbursts from thrusters. Once the thrusters run out of steam, the thing will crash. Which is kind of cool in a way.
It is fun to think about a Tesla Roadster sitting on the Martian surface. LOL
We're going 'redneck' decorate Mars. The next trip they are going so send a trailer home to sit behind it. Nothing better than a crashed car in front of the trailer. I'm savin' it for parts! Dangit!
https://www.popularmechanics.com/space/moon-mars/a16571489/elon-musk-space-tesla-mars/Musk's vehicle won’t be going to Mars, or even orbit around Mars. In fact, it could be several million miles away from the Red Planet. Rather, this launch would put the car into the kind of orbital loop that brings it close to Mars and Earth over and over again.
The Falcon Heavy launch would place the Roadster into a heliocentric orbit, meaning that like the planets and comets and so on, it will be orbiting the sun. More specifically, the Muskmobile will go into a type of heliocentric orbit called Trans-Mars injection, which it is the easiest and least energy-intensive way to move objects back and forth between Earth and Mars.
At specific moments every two years, the conditions are right to fire up the spacecraft’s engines and slide from one orbit to the other. A future transportation network that supplies a Martian colony would benefit from this kind of scheduling. Think of Musk's car like a city bus on a scheduled run through the solar system, slung this way and that to take advantage of the gravitational pull of the sun to make it easier to get into Earth or Martian orbits.
Since the Tesla doesn’t have thrusters, it won’t make that jump into Martian orbit. It'll be a Flying Dutchman, careening through the solar system for billions of years. Even so, the opportunity for a private company to launch anything on a jaunt through the solar system is itself a game changer. The fact that the launch may help lay the groundwork for industrialization and colonization makes this far more than a publicity stunt.