Well the WGA has vote and here are the winners:
Milk, Written by Dustin Lance Black,
Slumdog Millionaire, Screenplay by Simon Beaufoy, Based on the Novel Q and A by Vikas Swarup, Fox Searchlight Pictures
Waltz with Bashir, Written by Ari Folman, Sony Pictures Classics
Check out the rest of the winners HERE.
And it appears as though the Slumdog train cannot be stopped. After having now picked up the Producer's Guild, Golden Globe, Director's Guild, and now Writer's Guild, the film seems primed for Oscar glory with very little chance of an upset.