One of the issues with the WGA is they have strict rules who can be nominated and often an Oscsr Frontrunner will not qualify for one reason or another. That and the fact the SAG, PGA, and DGA all have had their say it's hard for the WGA to stand out. But this year with SAG, PGA, and DGA all going with different movies maybe we could get some help from the WGA.
The big winner and the movie getting the biggest boost coming out of the night is Spotlight. Winning Best Original Screenplay and to go with their SAG win it puts them a little ahead of the pack. But The Big Short won Best Adapted Screenplay to go along with their PGA win. The issue The Big Short has is that it will have stiffer competition at the Oscars especially with Room that wasn't eligible for the WGA.
I think the two will probably win their respective categories at the Oscars but still leaves Best Picture up in the air. Despite not being nominated for a writing Oscar The Revenant can still take the top prize and you really can't rule out Mad Max: Fury Road and the love people have for that.
Winning Best Writing for a Documentary was Going Clear the Scientology doc by Alex Gibney. Despite high praise for the movie it didn't get an Oscar nomination. And Amy still the likely Oscar winner in that category.