What happens in her life next actually depends a lot on what the storyline of DA3 and the role of the Warden and Hawke play in it, actually. If nothing else, assume that Etain finds Kathil eventually, and they travel together hunting down whatever it is that she's hunting down at the time.

(There's a oneshot in there of how Etain and Kathil end up getting along, and Anders's issues with her, that I may write some day.)

I will very likely return to Kathil one of these days, probably after we start hearing concrete things about DA3. Until then, she'll probably get some onshots, but that's it. :)