Excellent question! We're getting close to releasing part 2/3 of Tai Ming on Frontline, after which we of course have to make part 3/3.
Part 3 will be smaller than the previous zones, but will feature two bosses, one of which is really... weird. I don't want to spoil its design but Fred will have his hands full creating sprites for that fight!
We don't want to guess a release date for anything since we're so horribly bad at getting it right, but that's basically where we're at content wise! On a more positive note, Tai Ming is pretty massive compared to the other two dungeons, and I believe it will add well over 2 hours* of gameplay for most players when it finally does reach the Stable branch.
* if you run through it without farming and not talking with side-NPCs