Jim Lee's leaving the rebooted Justice League comic, his last issue is #12, releasing on August 29th, so he should be geting back to finally finishing his art duties on Dark Knight: Boy Wonder now, then it can be released on a monthly schedule.
http://www.bleedingcool.com/2012/06/05/jim-lee-to-leave-justice-league-position-available/
On August 31st last year Jim Lee was asked about Dark Knight: Boy Wonder.
Johnny Destructo: "I know you had spoken recently about ALL-STAR BATMAN & ROBIN...I know it's going to be DARK KNIGHT: BOY WONDER and that they are waiting because they're focusing so much on the (DC Universe) relaunch...but do we have a release date for that yet?"
Jim Lee: "No release date yet because once you say something, then you gotta deliver, and JUSTICE LEAGUE is my first priority, deadline-wise. But I actually have pages of ALL-STAR BATMAN & ROBIN done, but it just doesn't make sense to put those out unless I can deliver the rest of the story on a timely basis."
Johnny Destructo: "Oh, I thought that DARK KNIGHT: BOY WONDER was already done, it's not done yet?"
Jim Lee: "No, no."
http://www.aintitcool.com/node/51725
Jim Lee again confirmed on twitter on October 10th last year about the delays, "truth be told--not Frank Miller's fault. Falls 100% on me."