The game has been beaten...
...At least by two guilds. The first kill goes to SK Gaming though who managed to drop Kil'jaeden, the final boss of The Sun Well and The Burning Crusade expansion pack.
Having defeated Kil'jaeden they are essentially done with the World of Warcraft (until Wrath of the Lich King comes out).
We all know they will be back many times though farming gear for everyone else in the guild in preparation for Wrath of the Lich King.