Answering questions on Tumblr about previous projects she was working on for DC Comics, Gail Simone stated,

I might have meant the huge thing I am still working on, that hasn't been announced yet.

Curiouser and curiouser… one inquisitive soul asked Gail, and got a response,

Anonymous asked: Are the Birds involved in the huge thing you haven't announced? Yep.

Birds Of Prey, the female Bat-team of Gotham that Gail wrte for years… although will it have a Batgirl/Oracle? Because Gail had previously stated.

No, I think I am done writing Babs, but thank you for asking!

Curiouser and curiouser and curiouser and curiouser…. just a little bit of the Birds though, for a much bigger project. Still any return is always welcome.

UPDATE: Just to reassure…

I said I got to WRITE a little bit of the Birds for something. Which I did. That thing is not an ongoing book or even BOP-centric. — Gail Simone (@GailSimone) July 27, 2015