The biggest danger to the global enviroment is almost certainly global warming, not only from current consumption, but also (and most immediately) from already-spent fuels and pollutants. Humanity could disappear tomorrow and significant environmental changes would still occur as a result of this.
So what threat would the Planeteers face in a movie? Introducing a new, comic book-like threat would risk downplaying the aforementioned real dangers. The TV show was a parable for kids, which was fine, but unless they make a movie similarly aimed at little tykes (doubtful), such fables would almost certainly look incredibly silly to all over-14 audiences.
A parodic take a la 21 Jump Street *might* work... but this fan trailer plays the CP concept pretty much totally straight, and the result is suckage.