According to Star News, Jang has decided on the role and is currently finalizing the details. An A-list actress (yet-unnamed) is the top contender for the female lead, and once the rest of the casting is made official, the movie will begin filming.
This ought to be interesting — back when Kim Hyun-joong was supposedly headlining, I had been turned off because his acting is SO inadequate that it even got in the way of my finding him physically attractive; in Boys Before Flowers, my annoyance with the acting spilled over into annoyance with the character. But Jang Geun-seok is not only pretty, he’s got comic chops as well as dramatic ones. Plus, there’s the fun trivia tidbit of Jang taking over this role from Kim considering that he had initially wanted to play the Ji-hoo role in Boys Before Flowers (which, of course, eventually went to Kim).
(The source article says Jang’s casting is a done deal, but until I see other outlets reporting this news, I’m not fully convinced this is final. For what it’s worth.)