Yeah, the Black Label mini thing is just a rumor out of Bleeding Cool. Right now, the only things we know for a fact about 5G is the stuff from Wonder Woman 750, Flash 750 (has that shipped yet? It's supposed to be our next peek, anyway), and the 5 one-shots. Oh, there's supposed to be something in the free comic book day stuff too, I think. Everything else is unconfirmed at this point.
But I join you in hoping we get some good Nightwing in there somewhere.
Shhh! DC has convinced itself this is a fantastic story that's just too smart for fans. If you bring any kind of logic into things you'll damage their confidence!