What Happened to Cars in Pixar Universe

In the years of the Cars in the Pixar universe, the human race left Earth. Just as the toys in Toy Story come to life when people aren't around, so do the cars. But with one difference. This time there were no humans left on the planet and we saw them living in space in the movie Wall-E. But in the finale of Wall-E, humans returned to Earth after 700 years. But when they returned, the cars were nowhere to be found. So what happened to them? If you remember, the movie Cars 2 already showed us the resource crisis. We learned that the oil was starting to run out. As the planet ran out of fossil fuels completely, cars began to die on their own by the time they got to Wall-E. So maybe we will see Lightning McQueen and other cars disappear in the upcoming movies.