I have a feeling that facial expressions will only be present in scripted events (ie scare face on allied soldiers during the normandy landing), I doubt it if they can do it in real time like "when you shove the barrel of your rifle in their nose".
Then again, I could be wrong

And if I'm wrong, it will totally rock... okay, what am I saying?
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"Unplug all electrical devices and come out with your servo-mitts in the air!"