This is going to be a very telling announcement. With the expanded lineup and weighted ballot the PGA has probably overtaken the DGA as the pre-eminent Oscar precursor imo, and it was here that the "Hurt Locker" and "King's Speech" seasons were decided. "Argo" needs it the most imo because it's a populist, consensus pick and if the Guilds don't get behind it, then the Academy certainly won't. I think it'll win tonight, which does mean it should be offically considered our frontrunner, Affleck snub or no, but it won't decide the race just yet, "Argo" is going to need more than this.
If there's a spoiler I imagine it'll be SLP which is like LMS handled by the Weinsteins, ie: PGA material. The problem is I think the renewed BP hype and breakout BO for the film came a bit late for this group, but if the passion was there all along it could still happen and if it does I'll be about ready to call it for SLP. Likewise if "Lincoln" wins it'll almost certainly take DGA and WGA too and then that'll be that.