I did one with former SKT members, plus I'm bored af at work, so I decided to list all the players that participated in the 2012 Worlds and where are they now. If I'm bored enough again, I might do one for each year. Enjoy.
Season 3 version:https://www.reddit.com/r/leagueoflegends/comments/df09an/season_3_worlds_participants_where_are_they_now/
--NA--
---CLG Prime---
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Voyboy - Retired (Streamer)
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HotshotGG - CLG (ex-Owner) & Streamer
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bigfatlp - Retired (Streamer)
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Doublelift - Team Liquid
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Chauster - Retired (Accountant)
---Dignitas---
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Crumbzz - Analyst deck
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IWillDominate - Retired (Unbanned and streamer)
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Scarra - Retired (Streamer)
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imaqtpie - Retired (Streamer)
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Patoy - Retired (?)
---TSM---
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Dyrus - Retired (Streamer)
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TheOddOne - Retired (Streamer)
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Reginald - TSM (Owner)
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Chaox - Retired (?)
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Xpecial - Harrisburg University Storm (Coach)
--EU--
---CLG EU---
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Wickd - Retired (Streamer)
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Snoopeh - Retired (Streaming/coaching business or something)
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Froggen - Golden Guardians
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yellowpete - Retired (?)
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Krepo/Boris - G2 (Manager)
---M5---
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Darien - Retired (Streamer but with no stream schedule)
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Diamondprox - Gambit
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Alex Ich - Retired (Working as a software developer)
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Genja - Retired (?)
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GoSu Pepper/Edward - UOL
---SK---
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Kev1n - Retired (Streamer)
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Araneae - MAD Lions E.C. (Manager)
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ocelote - G2 (Owner)
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YellOwStaR - Team-LDLC (Coach)
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Nyph - ?
--Korea--
---Azubu Frost---
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Shy - Reitred (Mandatory Army Services)
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CloudTemplar - Caster
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RapidStar - Cloud9 (Coach)
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Woong - Retired (Works in his father's company)
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MadLife - Retired (Streamer)
---NaJin Sword---
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MakNooN - Streamer
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Watch - Retired (Streamer on Afrreca)
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SSONG - Free Agent
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PraY - KT
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Cain - Team Liquid (Coach)
--China--
---IG---
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PDD - Young Miracles (Owner) & Streamer
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illuSioN - Retired (?)
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Zz1tai - Free Agent & Streamer
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Kid - Retired (Streamer)
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XiaoXiao - Retired (Streamer)
---Team WE---
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Caomei - Retired (Streamer)
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ClearLove - EDG
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Misaya - Retired (Streamer)
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WeiXiao - Retired (Streamer)
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FZZF - Retired (Streamer)
--GPL--
---Taipei Assassins---
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Stanley - Retired (Streamer)
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Lilballz - Caster & Streamer
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Toyz - Retired (Streamer)
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bebe - Retired (Streamer)
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MiSTakE - Caster & CEO of M. Entertainment
---Saigon Jokers---
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QTV - QTV Gaming (Owner)
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Violet - EVOS Esports (Coach)
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NIXWATER - Lowkey Esports (Coach)
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Archie - Free Agent & Streamer
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Junie - Free Agent & Streamer
Small conslusion: Out of the 60 participants that played in the S2 worlds, only 12 of them are still in the competite scene (either being players or coaches).
Edit: Thanks everyone for the updated info.