(The detail that makes me most interested in Cars 3, frankly, is that one of its writers is Mike Rich, who wrote Finding Forrester and who also was the uncredited writer of Miracle. Not who I'd have imagined would write for Disney Pixar, but an intriguing choice.)
So in the spirit of having fun, I can picture it: one or two or five films from now, there'll be Cars in space.
We'd meet heroic rocket Glenn Mercury (or maybe Apollo Glenn!). We'd see Lightning McQueen in a somehow-fitting helmet. We'd learn that satellites are both alive and really good at holding their breath. Mater'd get space madness (too many cosmic rays, man). We'd see a car in the moon, well, really, what looks like a car, like how we see a face in the moon. Would the International Space Station be alive? I haven't worked that out yet, but I'm guessing not. (Ooh! It could be the International Race Station! Because racing! Even in space!)
Cars 9: Space Race. This could happen. Maybe with an exclamation point in the title.