I am concerned about the flying bison in the trailer. I dunno if we ever got an estimated lifespan for those things, but unless that's Appa living for 70+ years, then where the heck did it come from? Appa was the last, he had no one to mate with.
if you want info about the setting and characters we are about to see in that series you should follow this link here.
lots of things explained, and the bad guys look extremely cool

don't watch it if you are scared of (minor) spoilers,

spoilers!?
http://www.youtube.com/watch?v=azJBb9RHVZI&NR=1
spoilers!?