The choice is very clear.

Iroh is the only sensible choice to teach Aang firebending. Jeong Jeong vanished, Shyu vanished, and Zuko? :lol:  thats just laughable. :lol: that kid is in way to much turmoil to do anything right now. he just betrayed Iroh, taking sides with Azula. he feels as if his honor has been restored. theres no way he will risk everything he ever wanted to teach the Avatar. Iroh already has helped the Gaang. he knows that balance needs to be restored in the world. he knows how to teach, knows the importance of being calm and NOT in turmoil *coughcoughzukocoughcough*

so all you Zuko fans, sorry. not gonna happen.