1. I know someone has already used this but aang and katara should get together cause of the last part of the desert. i mean really, no matter how mad you get, you just cant hurt a loved one or someone you like.
2. remember in the avatar state, when aang goes thru a lot of stuff with general fong to try to ignite the avatar spirit but it fails and he and katara are talking, katara says "im not saying the avatar state doesnt have incredible and useful powers, but you have to understand, for the people who LOVE you, seeing you in that much rage and pain..."
so katara just sort of hinted that she loved aang.