So far, all of you are incorrect, the nomads arent peaceful nor warlike. Sirius is their home, basically it was almost completely designed for them, the Library on Manhattan, Cardamine and so on. All they want is for the humans to leave basically. By force, manipulation or any other mean that they can achieve. They're not seeking to eradicate the humans, just remove them from Sirius.
Edit: Anyhow, refraining from guessing till the Lore comes out is best you can do really.