Right, there is no "Pharaoh, let my people go" Moses syndrome going on here. Is Bungie working in slave like conditions? They might be, but we would have no way of knowing. If they were tired of working on Halo, I'm sure they could very well move on to something else. Still, I don't think there is any indicator that they're absolutely done working on Master Chief's story. If I remember correctly, Bungie has stated that there is an Epoch's worth of fiction written for the Halo universe. Who knows, they may still be very enthusiastic about continuing the story.