Before I start going into detail I wonder what people are expecting in the way of humanity's re-emergence. I'm personally thinking of factions along the line of those present in STALKER: Peoples united by their various views of how the world should be run. For example in STALKER there are bandits (self explanatory), the Merc Faction (enemies of everyone, working just for money), Freedom Faction (believe the "zone" should be accessible to everyone), Duty Faction (believe the zone should be closed off and studied carefully) and the Monolith Faction (religious zealots basically).
So what do people envisage as potential factions in this new society?