I mentioned this rumor before but would it work from a logical standpoint?
Many were bothered by the fact Damian won't be in BaRE for some time. It was assumed that he'd find out Dick was alive when he arrived halfway in...only he found out in Grayson. Now originally Robin War was just about Damian being the one to confront the WAR Robins. I think this was supposed to keep him occupied before he showed up in BaRE. So the rumor was that Damian or Cassandra are going to be the new Nightwing. Techically this could work and would make more sense if he didn't find out Dick was alive prior to the event.
The problem? Wouldn't his book need to relaunch AGAIN with a new title? I also doubt many will be thrilled with the idea of Damian ditching the legacy for newbies even if he's picking up another legacy from Dick. It doesn't really make sense for him to give it up so readily for complete strangers (or just Duke) who aren't even skilled.
The Cassandra rumor actually fits a little better since her new origin seems to tie into this big secret with Dick. She's said to have a big part so maybe they bond enough that she gets inspired by him? I'd prefer Black Bat but it doesn't sound like we'll getting that.
DC seems to be sticking with the spy thing so it doesn't look like we're getting him back as Nightwing anytime soon.