According to the overview trailer you'll meet federation troopers "occassionally". I'm pretty sure Miles will only be around during the early game, but there will be other NPCs later on. Does sound like you'll be alone most of the time though. I'm not a fan of what I've seen of Miles at all, but I do enough have faith in retro studios to be sure that they won't give us a quippy sidekick for the entire game.