I'm one of the biggest Vader collectible fans out there, but I'm actually hoping that they don't do Vader first, simply because they've got the Vader statue coming out soon.
I haven't been very impressed with the facial sculpts of Luke and Han for their statues, so I'm not sure they can pull off human busts. I hope I'm wrong though.
I'd love to see them do creature busts, like Chewie. They'd be a lot more interesting (unless, like I said, they can improve their human sculpting).