The last sentence is what matters. I don't really think that the Brewers will (or should) bring Cordero back, but we do have two weeks to give it a shot.
As I understand it, filing for free agency is little more than a formality. Doing it now is really only a way of saying, "I may like it here, buddy, but I'm not going to let you pay me the minimum."
Miller probably filed because he (rightly) sees Ted Simmons as a threat to his job.