Our LS was talking about this a couple weeks ago and more or less came up with the exact same prediction as OP. Some are unsure if the 'friendly' beastmen will get a primal but I think they will. Afterall, while the Sylphs have helped us figure stuff out in the main storyline, so do moogles. Moogles are by nature friendly too... So I think we WILL fight a Sylph primal. We also guessed them to be lightning...and feel the fight might be in the Moonspore Grove that is right next to their village.