Cross Distant Finale with Improbable Age, sprinkle a little Future Badass and leave to simmer.
When a series involving young characters skips ahead to the future it will rarely be more than a few years into the future (unless Time Travel is involved of course), which keeps the characters fairly close to the people we know, and saves on the age makeup. Such is the temptation to show where the character ends up however, that many writers show the character already well established and very successful in their chosen career, even if only a few short years have passed and logic would suggest they should still be somewhere at the bottom, working their way up.
In extreme cases the character, who has barely started out a particular path before the time skip is at the very pinnacle of their profession when we rejoin him four years later. Compare Alternate Universe Reed Richards Is Awesome. It can be justified if the future self was using Time Travel for Fun and Profit.
Contrast Future Me Scares Me and Future Loser.
Kind of approached from the other direction in Night Watch. Vimes, a happily married man awaiting the birth of his first child, an alcoholic who has very successfully quit drinking, one of the richest people in Ankh-Morpork, a duke, at the top of his profession and one of the most powerful people in the city, goes back in time thirty years, meets his eighteen-year-old self and realises what an idiot he was.
Brooke Davis of One Tree Hill has become a millionaire leader in the fashion world by four years after graduating high school. She runs her ultra successful clothing line, magazine and tv channel at the ripe old age of twenty two.
Dawson Leary of Dawson's Creek is the creator of a hit television series based on his life by the age of twenty-four or twenty-five.
Nathan Petrelli of Heroes will make it from newly elected Congressman to President in less than five years. Even given the example of the current holder of the office that rapid a rise seems a little bit of a stretch, no matter how many (pot) pies Linderman has his fingers in. But perhaps not so much of a stretch as:
In Charmed (episode 2 season 2), the sisters travel 10 years to their future selves for a day, and Prue finds herself the super rich owner of numerous big successful auction houses over the word. Subverted because they change that future from happening, and later made impossible because of Prue's early death.
One episode of Boy Meets World had a Flash Forward to seven years in the future in which Jack has become a "captain of industry" despite the fact that he would only be 27 or 28 at that point. However, this sequence is not canon and is implied to be an extended Imagine Spot in Eric's head.
Bones is extremely successful without time travel, but at her high school reunion she just can't do her usual thing of casually bringing up the fact that she's very sexually attractive/intelligent/wealthy/famous despite (or perhaps because of) Booth's coaching.
The Grand Finale of Desperate Housewives gives this type of ending to each of the main characters (except Susan, whose fate is left unstated): Lynette becomes CEO of a multimillion-dollar company in New York and buys an apartment overlooking Central Park, Bree moves to Kentucky and is elected to the state legislature, and Gabrielle starts her own fashion website and TV show, moves to California with Carlos, and buys a mansion.
Done twice with the player character in Grim Fandango. First, Manny arrives in the port town of Rubacava and takes a job sweeping up in a nightclub, which he owns a year later. Then he leaves and begins washing decks on a ship. After another year, he's the ship's captain. We have no idea how he managed to accomplish both, apart from a missable line near the beginning of the game:
Manny: I wonder if I would be happier on a ship? Then again, I'm so competitive I wouldn't rest until I became captain.
Subverted in Sluggy Freelance when Torg starts acting all smart and educated after some information a Time Traveler left behind indicates he becomes a world famous professor in the future.
Riff: Actually he's destined to play "The Professor" in a musical version of Gilligan's Island and the Demon is going to force the world to watch. (shudder) I just didn't have the heart to tell him.
Rayne from Least I Could Do witnesses a great future for himself during a hallucination - he takes over the company after Marcy, has a mansion shaped like Minas Tirith, lives with his favorite niece, still has all his friends, and grows a beard worthy of Sean Connery. It's a justifiable exaggeration as it's his fantasy.
Ben of Ben 10 runs into two version of his future self, Ben 10,000, from different timelines, one in the original series and one in Ben 10: Ultimate Alien. Both versions have a Badass Beard, are quite buff and good-looking, respected as heroes throughout the universe and can wield their shape-changing devices to their full potential. Justified in that Ben is already working towards achieving such a future even before meeting his future self.
One of his future self also hints that his cousin Gwen became President of the United States.
Lisa Simpson was President of the US at the age of 38 in a glimpse of the future in The Simpsons. Okay, she is a genius, but that is still five years younger than Kennedy, the youngest person ever elected President, and he was a war hero. Lisa is also an unmarried, vegetarian Buddhist. She must have had one heck of a campaign manager... Then again, it's mentioned in the same episode that she is the first heterosexual female President. Subverted however as some of the stuff she did turned bad, and she is in knee deep of debt.
Bart's future career path in the several flashfoward episodes goes from a garage band member to unemployed stoner to demolition man to law school student to (down the road) Chief Justice of the Supreme Court. Apparently the Simpsons become the next Kennedy family.
This can happen to bad guys, too. In the Danny Phantom episode "The Ultimate Enemy", we learn that—at the age of about twenty-four—Danny is now an evil half-Vlad, half-Danny mutant who has taken over Amity Park and rules it with an iron fist. And by "rules," of course, we mean "punches."
Hell, as the movie starts, it's heavily implied that Amity Park is the only place he hasn't taken over. Managing that is merely his Establishing Character Moment.
Accidentally subverted by Cartman himself in South Park. A successful and healthy man appears, claiming to be the future Cartman, and tells his younger self that he's just started on the path to wealth, success, and happiness as long as he becomes nicer, goes on a diet, works hard, and stays away from drugs. However, because the episode focused on parents trying to scare their kids with actors posing as Future Loser versions of themselves, Cartman doesn't believe a word of it and says he'll start acting even worse just to spite him. The instant Cartman walks away, the future Cartman transforms into a poor, fat slob.
Nicely averted in Family Guy where Stewie meets his 30-odd year old self and is appalled at what he finds.
In Rocket Power, Reggie flashed ahead about ten years and was a publishing mogul living on top of a skyscraper- at about 22.
Which becomes Hilarious in Hindsight as, judging by the original air date, her imagined success coincides with the decline of the magazine industry.
Subverted once again in Jimmy Neutron where Jimmy screws up the future by giving a megalomaniac complex to Libby, which twists the futures of Carl, Sheen, and Jimmy into a fashion outcast, a Dumpster diver, and a dimwitted loser who's married to Cindy, respectively.
Although, the original futures they viewed for themselves (before they screw it up) are this trope played straight: Jimmy's won the Nobel Prize in every category, Carl's a professional llama breeder whose llamas can breathe underwater and talk, and Sheen's a fashion model so popular that (according to Jimmy) it's headline news whenever he changes his socks.
The title characters of Phineas and Ferb don't actually meet their counterparts when they go twenty years into the future, because Phineas is in Sweden "for the awards ceremony"note The Nobel Prizes are awarded in Stockholm while Ferb is at Camp Davidnote The President's country retreat. (Note that Ferb is a naturalized Briton, so part of the Constitution might have changed.) Given what the pair can accomplish in an afternoon, this is hardly surprising.
Also, Stacy is President of Uruguay. Interestingly, Word of God says they came up with an explanation for how this happened when somebody at the studio asked them about it, but didn't reveal what.
The Invader Zim episode "Dib's Wonderful Life of Doom" has Dib, after receiving superpowers from alien shoes, defeat and imprison his Arch-Enemy, expose every single secret supernatural creature, single-handedly repel an alien invasion, and receive the "Greatest Person Ever To Live" award, all within ten years of his childhood. Subverted when it's revealed this is nothing more than an illusion crafted by Zim's Lotus-Eater Machine.
In Ferpect Crime, the main antagonist becomes a rich designer in just enough time for the main character to grow his beard. He unbelievably falls for her then.