I have a theory about Renee. First, I'm taking the not-so-revolutionary stance that "Renee as a KGB agent or other impostor" is a red herring - but not a pointless one. My suspicion is, this was all a way to get us interested in her so we care when SHE is the one who finds out the truth about Philip and Elizabeth (or at least overhears much more than she should) - meaning that of course they have to kill her. Stan will have some inkling that she died because of something related to his counterintelligence work (shades of Amador), filling him with both guilt and a red-hot passion for catching Russians. Can the showdown with his friendly neighbors be far behind?
Meanwhile, this could be the last straw for Philip. He's having a tough enough time killing innocent strangers. How much worse will it be when it's someone he knows?
Now it becomes a matter of: which will happen first? Will a vengeful Stan crack the case, or will Philip simply crack? Or will Claudia/Elizabeth/"The Center" try to yank them out of there before the sh*t really hits the fan?
Just a theory; not claiming any psychic powers. But could happen, no?