Who do you think is going to be the voice of Iroh in season 3? I have no idea, according to Wikipedia this guy was Mako's understudy at one point. He has big shoes to fill. Mako was excellent in this role. He really captured the emotional element of the character. The pain Iroh feels for the death of his son, and how he cares about Zuko, he did it perfectly.
I can think of any older??actor that could do that at the moment? Maybe the person that voiced Juong Juong, Kerone Young could do it. He has experienced playing that role, opposite Dante Basco the voice of Zuko, on Disney Channel's American Dragon: Jake Long, but I seriously doubt he could capture the emotion of Iroh.
Yesterday I saw the "The Tale Of Iroh" in the episode "Tale Of Ba Sen Se", at the end when he visited his son's grave on his birthday, that was so sad.