Her deal with Bracken is that she won't release the material in the file unless he fails to leave her and hers alone. If she nails him, it won't be for anything related to her mom's case or the mafia blackmail kickbacks unless he calls out the dogs again. However ... the guy is as crooked as a corkscrew, so there is probably something else out there that could be used against him -- if she finds it she just needs to leak it to the US Atty's office or a reporter somewhere, and nature will take its course.
All I have to say to the writers is: please, don't tangle up Castle's father in the Bracken matter. That would be too anvilicious -- let Castle and Beckett each retain a separate past.
As to Dorn coming back a few more times, that makes perfect sense. Other than Castle and the boys, he is the only one she can talk to about the Bracken situation, and then there is that whole business of her inability to commit.