I doubt it personally. I dont think guilds will be covered, but instead general gameplay. I could be proven wrong though.
If they've been holding off due to tweaking some of the factions, etc., I would imagine at this point they should be pretty decided which factions will be in the game, no?
I'm sure there are a lot of mechanics and smaller details they are still playing around with, but I would be surprised if they are still coming up with any entirely new factions between now and their content lock date.