I think the bigger question here is how did Johnson know that Novak was investigating Wilson's claims to begin with? Who had Novak talked to before that street encounter that made it so that Wilson & Johnson knew to spring this "chance meeting" into being??
We may find out this week. I think Libby and Rove are "safe". Reminds me of the famous line in "Absence of Malice". "Mr Libby you are a very smart man,..don't get too smart."
We could get a conspiracy to obstruct justice against Wilson, Plame, et al.