I was talking to my friend about this, but I really wonder what they can do for a final conflict in this season. It seems kind of bizarre in hindsight, that they would use something like Harmonic Convergence in Book 2. That is a very substantial plot within the world of Avatar. You could argue, it's even more important than Aang vs Ozai (it wasn't executed as well, but in terms of the scope, and the impact it would have on the entire world. Also how long running this battle is, and how it determines the entire world moving forward).
Point is, something like Harmonic Convergence is HUGE, and would have been a good way to end the series. What can they possibly do to top that? Normally I would say, they wouldn't need to. But since this is the end of the entire series, I feel like they have to do something to kind of solidify Korra's legacy. It can't just be another mini-side conflict like Zaheer right? Doesn't it have to be something big, that kind of is the final statement for this character? So what could possibly happen in the world (conflict wise), that ends up being her final challenge? Or at least, the final challenge the audience gets to see with her....
And even on a character level, I just wonder what they can do, to kind of get everyone into a final place with the series. I know it's already too late for all the side characters to have this done meaningfully. But still, they have to do something...right?