How much of the story content is currently available?

We are tasked with finding the 7 arks, each representing one of the gods that ruled over Arkesia. So far we are able to collect 6/7 of the arks, so does that mean once we get the final ark, the entire story will come to a conclusion?

In other words, if I just play it for the story like a casual single-player RPG game, how long do I have to wait for the entire story to finish?