Just curious, why did you place spoiler code around conjecture on who the person watching Carol might be?
In any case - I'm not sure you're right because the preview for next week's episode has the person you mentioned elsewhere currently.
Oh, I just figured maybe some people might not be aware of the actor being in this season's episodes, so figured I would err on the side of caution. You never know when someone's going to get their knickers in a twist.
I never see the previews either, so that's information I wasn't privy to.