There is no mandated reporting by therapists about a patient who is a pedophile. Just being a pedophile is safe to reveal to any (decent) therapist,

And just how common are these not-decent therapists? Pretty common, since a lot of them feel that all pedophiles will molest children sooner or later. If you're convinced of that, why not start harassing them now?

and they are only mandated to report a pedophile who has indicated he is about to break the law and even has a victim in mind.

I'm afraid it's not that clear. "Indicated he is about to break the law" surely doesn't require that he say as much. The therapist is allowed to decide it is likely based on her own judgment. Describing feelings of attraction could be taken as being about to break the law.

You should check jurisdictional differences. Of great interest, in California, admitting to looking at child porn is a mandated reporting offense.

I blogged on this here:

http://celibatepedos.blogspot.com/2014/07/keep-kids-safer-get-rid-of-mandated.html.

As I pose in there, the therapist is faced with a trade-off. Dire consequences if the pedophile does molest some child. What if they over-report when there was no danger? Really no consequences at all. What are the chances a pedophile will win a lawsuit against anyone?