Actually, the thought of Zuko teaching Aang Firebending seems probable to me. I mean, he only betrayed his uncle and joined his psycho sister in the invasion of Ba Sing Se and almost defeated the Avatar gang, but I guess he could change. He'll probably ditch his sister once he figures out what he wants and help Aang Firebend, with the help of Iroh of course. I mean, they did have a few moments of peace throughout the first two seasons; like in the episode where Zuko actually catches Aang in the Northern Water Tribe and they have to shelter in that cave, and when Aang and the Blue Spirit escaped from Lake Laogai and the Fire Nation. Not as much animosity in those cases.
Oh, and welcome DarkIllusion!