....make me smarter

So. Most of you know about this show.   It is an amazing show. I love it much.
Sadly, most of you know about this show.  If is a terrible show. I hate it much.
Some of you may know this show.  It is going to be so dang amazing.
I am going to love it. so much.  It is going to be on Nickolodian. Or whatever it is called... but thank GOODNESS for Hulu.

When I was reading the plot stuff... I came across something I did not understand.  The waterbender who is going to be the new avatar needs to learn airbending. She learns it from Aang, Katara, and their son, what'shisface.
I thought that in order for their to be a new avatar, the current avatar must die.
I'm not saying I want Aang to die or something...
But in order for the new avatar to come, Aang should be dead right?
I am just so darn confused.