Joe Manganiello's instagram has been an interesting source for Batman rumours, as the actor goes about researching his role of Deathstroke. Nothing too big, but little hints at tone and story could be gleaned if you read too much into everything, as us media types are want to do.
However, this next one seems pretty big. He has just posted a photo of him next to Anna Kendrick with the caption:
#Deathstroke and #Robin
Take a look:
This has of course lead to specualtion that Carrie Kelley might be in the film.
I wouldn't pull the trigger on expecting this though. Kendrick has recently been seen in interviews with director Ben Affleck jokingly campaigning for the role, so this could be a call back to that. Also, Kendrick is certainly a bit older than Kelley is usually portrayed, so that is another potential thing against it.
Neither of these things rule out the possibility though, so it could be true too. Hard to say right now. I'm sure we will find out before too long if it is the case.