I don't think we even have the act 1 in its entirety though. Cause there are a few routes on the surface which are blocked for the EA. And as far as I understand the story, there is only one way out of act 1.
I was wondering about that too. When I got to the end of act I it seemed a little surprising where it ended--it didn't feel like a complete act. I'm used to act I's having some sort of turning point/pseudo-conclusion that sets up more story. But, that could also be because we haven't seen what's next.
