It's been rumored for a few weeks now, ever since Spike Lee's announced that he was remaking it, but now it's official - Josh Brolin will play the "Oh Daesu" role in the OLDBOY remake. That's good casting, in my opinion - Brolin proved in W. that he ages well on screen, and I think he'll bring the intensity to the performance that we're all wanting to see.
Now who for Woo-Jin Lee, or his Western equivalent? I've heard talk about Christian Bale, which would also be good casting if he'll take the part. But there's so many actors who are going to want to be involved in this one that it may just be a matter of first-come-first-served. It's also unclear, still, whether this will be a remake based on the manga or the film. But I'd love to see Spike Lee's version of the hallway scene. Although it's hard to mess with perfection, and that scene, as shot, is perfect. I don't think anyone would argue that.