Given the book's current sales, I'd assume we won't be seeing Kate for a while. Certainly if Gail Simone's excuse/reason for the absence of Steph' back in the early days of the New 52 are to be believed. When asked about DC's stance on Steph at that time, Gail posted the following response on her tumblr;
"This sucks, but Stephanie's book was not at the sales level they were hoping for with a Batgirl logo on it. This gets lost over and over in the timeline, but her book was already going to end before the new 52 thing happened. When that happens, there is usually a period where the character is deliberately held back for a while. It is NOT to be mean, honestly. It is to prevent bringing a character back in a method that doesn't change enough from what they were when they were cancelled.
There is even a not-too-pleasant term for it, "waiting for the smell to wear off.". If they don't do that, if they don't reposition properly, they are almost certainly setting that character up to fail again."