There's an angle to this story that hasn't been covered very much. One of the two reporters facing jail terms (I believe it was Miller) originally defended herself by claiming that she never spoke to anyone directly -- she had obtained the information about her article from Novak's article. Her story fell apart when it became clear that her article had included some specific pieces of information that hadn't been in his original piece.
"Novak revealed the name of his source to the prosecutor..."
Well, then why isn't the investigation over? What you say makes sense, it is congruent with the article's discussion about a "Martha Stewert prosecution". But if there was a crime committed, wasn't it by the leaker? So, if they know who that person is why hasn't the focus of the investigation turned to him or her?