It'll be great to have more stories from that universe, but why that storyline? There just isn't a way to make it compelling. We already know that all of the characters live until old age and the only one who dies is Aang, but not because of any conflicts.

At best they will be able to do a coming of (adult) age drama, but coming of age stories were already well covered by both of the series.

In a universe that has literally hundreds of super heroes, most of which have legends attached to them, why not tell some of those stories?