Well, I could easily see a few assosiating with the freefolk. They enjoy celebrations, so I could see them slowly showing up at various celebrations across the world.
I could see (and run) and adventure to explore where they are from and meeting them. Also, on a broader arc, as they become more well known, I could see the desert people to the south and perhaps even the dwarves to the east beginging to encroach on their lands and suddently they're forced to defend themselves or flee, but that would probably be more of an issue as more of the world develops.
I do have a few PC ideas to play with them (I'll only get one, I already have 2 other characters, and i like both of them), and I'm sure others could find a concept to play with them as well.
I've always viewed fantasy with strange an unique races, often that have little corners of the world. In a way, much like lizardmen have their swarp somewhere, the Katara have their forest somewhere. I guess the problem is that, as cat people, they are easier to look at as light hearted or cuddly. And it probably doesn't help that much of their culture I've focused on is festivities. They are fierce wariors and hunters. They study magic. They worship gods. They even fight amonst themselves at times.
I know that I am capable and willing to make any character concept (class wise) work as a Katara, and it's not too hard, and that I feel makes them a fairly complete race.
I know I can't integrate them into Enworld by myself, so hopefully there are other players or GMs willing to use them as well, which would help expand their culture and influence.