Sooo...i'm going to assume Aang will live at the end of the series (it will be devestating if he didn't).
I also do not see Zutara happening for two reasons.
1. I just can't see Aang defeating the fire lord, to get his heart broken by Katara. After all the stuggle and the weight of the world being forced upon Aang's soldiers, i do not think the creators would create this devestating blow to his heart. (And yes, i do think he has had more struggle than Zuko in some ways. Don't get me wrong, BOTH have had immensley difficult lives, but Aang lost his entire world. He lost his people, his friends, and everything he knew was gone. Then when he wakes up, he finds out that he has left the world in shadow for 100 years, and has to defeat the fire nation basically single-handedly at 12 years old. How could forcing all of this responsibiliy and pressure not bring about a difficult life for him?) As i was saying...if Katara choses Zuko over Aang before the comet comes, it is just added pressure that Aang does not need. I do not think Katara would do that to Aang, she would not intentionally make his mission harder for him to accomplish. If Katara chose Zuko over Aang after the comet came, then it would devestate him when he should be rejoicing. How would you feel if you fought for the world and put yourself in danger for one girl, who then turns you down for your friend? (From N&DD: "I'm doing this for you, Katara"). i just can't see it happening.
2. As much as it is hard to believe, this show is in fact aimed for a much younger audience than are on this forum. Yes, most people that probably watch Avatar are older than the intended market, but the point is, the intended market is 6-11 years old. Now, my point. I can see Zutara working if it was intended for an audience like on this forum, but its not. I just can not imagine explaining to my 8 year old cousins (who love the show) how Katara could possibly chose Zuko when Aang loves her and Zuko has Mai. The hero always gets the girl, and if Aang isn't the hero and Katara isn't the girl, i don't know who is. I just think that if Bryke have truly made the story to stick to their intended audience, then Zutara doesn't have a chance.
I admit Zutara has some valid points, and Zutara is fun and all, but i just don't see it happening, Then again, maybe i'm totally wrong.
Just my two cents.