Yeah the light/void is almost guaranteed to continue into Midnight just off what we know. Sunwell and ... midnight. But I think Beledar will need to be resolved in TWW and I doubt this expansion will end without a more direct conflict with Xal. So when I'm saying Light/void, I don't mean it's resolved, I just mean thematically that's what I'm expecting it to be.
To me the deeper into the world part will be undermine, harronir elune tree roots and some sort of Titan defense force (like those big robots in Dorn for the skyriding WQ and the world boss).