I do have 4 main story arcs planned. We're currently in the first arc, the Janitor Arc. The next arc, which starts after the end of Chapter 6, is the Security Arc. Following that will be the Counselor Arc, and somewhere along the line we'll enter the Ambassador Arc. I may have a couple more between Counselor and Ambassador, and I'm not 100% on the Ambassador Arc, but each storyline will have its own main antagonist and plot hooks. Kind of episodic, I suppose.