it is going to be interesting to see which way LucasArts goes with this. Vader has to escape somehow. Will there be the dark clone coming out of the woodwork to free his boss, will the original starkiller show up out of the blue and, do . . . something.
In order to stay canon, and not completely derail the entire franchise, they need Vader free, they need the rebelion to remain intact, and they need to kill off Starkiller and all his clones. I am hoping they don't screw this one up. I think they could have found a less preposterous way of telling a story in TFU2, but it's far too late for that.