When asked by MTV if CW or Warner Bros. had approached him about playing the role of Ra’s al Ghul on the CW TV show Arrow, Liam Neeson said neither had, but he very quickly added that he would do it “in a heartbeat” if asked.
Neeson previously played Ra’s al Ghul in the 2005 film Batman Begins, directed by Christopher Nolan. His incarnation of the Leader of the League of Assassins (or League of Shadows in the Nolan Trilogy) also made a cameo appearance in the 2012 film The Dark Knight Rises.
As Neeson said, neither the network nor the studio has approached him about the role. This story at the moment is simply a what-if scenario. The trailer released at San Diego Comic Con featured a cloaked figured, assumed to be Ra’s al Ghul. It, therefore, appears that someone has already been cast in the role. However, no face was shown. It is possible that Neeson could still reprise the role, but it is highly unlikely.