(Spoiler alert for those who have not seen the end of season 2) Halfway through the episode 4 asks Milo what is coming onboard the ship and Milo says "one of you will betray the others" and says he isn't talking about the past with 6. "I'm saying it will happen again".

I didn't see what he meant by this. Of course they turned Milo back over to the seer ship. But that wasn't one betraying the others.

Was he talking about 4 when 4 stole the blink drive from the Raza at the end of season 2? That is the only thing I can think of. Nobody else betrayed anyone.