It's funny how whenever people discuss the possible future jobs and careers of Arthur and the gang, inevitably, somebody suggests one of them is going to grow up to be a serial killer. :p
I agree, Buster's going to end up being a bum when he grows up: his mother smothers him, it's going to ruin him for life, and he's not going to be able to face the real world when he grows up, because he won't be prepared mentally or emotionally... not that I'm speaking from experience or anything... Interestingly enough, it seems like a lot of fans picture Buster becoming a stoner when he grows up, lol.
Here are some of my own thoughts:
D.W.: Now, I'm not exactly sure about the adult world, but I can see her turning into something of a high school bimbo, hooking up with boys then dumping them and moving onto others on a weekly basis... I only think that, because I remember my niece used to be kind of bratty when she was a little girl like D.W., but then she went through a phase recently when she hit puberty.
Brain: Probably end up working at NASA, or some establishment like that, though I have no doubts his intelligence will make him a billionare in the future. Heck, he could probably even be the next Bill Gates or Steve Jobs and end up revolutionizing the computer world in ways neither Gates nor Jobs have done before.
Fern: She'll be responsible for the next TWILIGHT-esque saga craze that makes teens (especially girls) crazy.
George: A craftsman, carpenter, architect, or blues singer.
Binky: Possibly the next Billy Elliott.
Muffy: She'll probably TRY to become a successful fashion blogger/designer, or even the next Hoprah Windseed, but because of her lack of common sense as well as her ridiculously high and irrational standards, she'll only be setting herself up for failure. But then again, being independently wealthy, why would she need to work anyway?
Sue Ellen: She'll either become a politician, dabbling in foreign policies and such... or she'll become the next Chuck Norris.
The Tibbles: They'll be in jail. They'll spend a LOT of time in juvy, but eventually, will be guilty of a crime where they'll be tried as adults because of their past offenses as teens.