This might have gotten rebuked by the previews but....
What if Stan's girl IS a russian agent? She's trying to get in a government agency just like they are trying to get Paige in. It fits their M.O.
Stan figures out the Phillip Elizabeth thing and kind of hints to his girl what he thinks or she picks up on it.
Right before Stan can go to work with everything his girl murks him.
We get the staisfaction of him finding it out, but they get off free. I don't see them both making it out no matter what goes down but this finale could be on some Breaking Bad levels.