What if the boys grow up? Well, they won't but it's cool to imagine.
Cartman-He might become nice and become a realtor or something like that. Present day Cartman despises him future self.
Stan-First of all, no matter what your !@#$% ^&*() South Park fanon says Wendy and Stan will never make it. Stan could go to ways.
1.Becomes a middle class citzien.
2.Has a T.V show which is just a parody of South Park which Stan says is his personal adventures.
Kyle-He might become a lawyer just like his dad.
Kenny-Well, you know.
Butters-I have no idea but my guess is homosexual.
Jimmy-Leads a handicapable march for cripples in Washington.
Clyde-Nobody cares.
Craig-Jail time.
Token-He's black and rich now, he will be black and rich later.
Wendy-Since she is a somewhat liberal she might become a politic.
Timmy-TIMMAH!
Mr. Garrison- He gets fired because he sucks at his job.
Chef-He returns.