The art of bending:
Possible: Doubtful. Thou those monks in the east (just about any religious following) can do some freaky stuff. Ive seen a dude stand on his index fingers.
The bending in the show is built off actual martial arts, but they don't have the elemental addition. And the sub-elements aren't really sub-elements, except lightning. The ice is melted to water, and the plants are controlled by the water in them. Rather like bloodbending, which is actually control of the 70% water in our bodies.
That answer your question?
Well, Ozai(?) didnt die like he was supposed to. The gang fled, and then Zuko left to I assume join them. I didn't put that in spoilers because everyone reading this thread should have by now seen DoBS.
Oh, and sorry for the double post! ^^;;