I just saw a new commercial for the finale! It was Katara-centric, with her narrating. She was like, "When I found Aang in the iceberg... (something about him being the Avatar).... But I never realized how close we'd become." As she said that, it showed the kiss scene from DoBS. Then she said, "Now I know he has to face up against the Firelord. But I'm not going to let him do it alone." And then the narrator said something like "Watch destiny unfold in Countdown to the Comet!" That was when I squealed.
Sorry about the lack of detail, I was really too busy hyperventilating to pay REALLY close attention....