Well, we finally have an answer, straight from series artist, Chris Burnham, who states:
The current plan is for Grant and me to do 12 issues to wrap up his Batman super story, then I think the book will continue much like Batman & Robin has. But I really think it's a little early to be asking these questions. The first issue hasn't even come out yet and all you guys want to talk about is what happens in number 13!And there you have it. Personally, at times, I think I'd rather have it end. Part of me believes the series is just too closely tied to Morrison's grand plan, that someone else picking up the title would diminish the title's impact, so to speak. But at the same time, I don't want all the characters to just vanish, and you realistically can't just go "alright, we're done with that, no more international Batmen." It's just such a grand concept, you can't really take it back.
Nevertheless, we don't have to worry about that until Februrary 2013, when issue #13 would be solicited, so no point in worrying about it now.
(Source: CBR Forums)