I came across something on IMDb which states that Gorkil the Goblin King will appear in The Hobbit: The Desolation of Smaug. It says that he will be played by Barry Humphries.[1]
It calls him "Gorkin the Goblin king" and says that he will be a successor to the Great Goblin.
another link to Barry Humphries IMDb page [2]
showing his role playing Gorkil in The Hobbit: The desolation of Smaug
i think that when thet call him "gorkin" is just a typo or mistake.