How does Hank expect to bring down Walter without pretty destroying his own life? Arrest and imprison his wife's sister & brother in law. How does Hank explain the drug money paying for his therapy? He will look like he knew all along.
I'm assuming he is going to start doing some PI work, then find some stuff out. The people Walt works with will know, and Walt will have to choose between saving Hank's life, or keeping his secret safe.