[Atrocities]

In a recent episode, (SPOILER) Baltar provided some info about the expected survival rates of man kind. It was not good. I think they would all need to find a planet, a safe one, and then all settle it in order to give rebirth to humanity.

Ideally, I suspect that at some point it will become a virus war or simular. It is really the only option to beat the organic based machines of the cylon empire now.

Also it could be written in that they find other human occupied worlds, like they did in the origal series, and spark off a little side war. No one wants to take on an enemy of someone they don't know especially if that enemy has big powerful nukes and wants to purge the galaxy of man kind.