What most possesses my mind is when Katara says that "most" of her friends have died, and while I was sad, note she didn't say "ALL."

Someone from back then may still live!

My headcanon says that secondary characters still live.... and also Azula.

What I'm also looking forward to is the dichotomy of spiritualism vs. materialism, which would be incorporated with traditionalism vs. modernism. I think there's a hidden meaning as to why Korra had already learned three elements since as a child, which could be an intentional part of the Spirit World which acknowledges the world becoming more united.