Given how heavily Blizzard is teasing a Tyranny of the Light expansion since the Xe’ra thing in Legion, and the fact that the Alliance’s core religion involves the light and the Scarlets are coming back…
I think we all know it’s scooting itself towards the later. I’d actually put money on it since Blizzard has a pattern of putting a faction big bad in power the expansion before they drive the villain truck off a cliff… and Turalyon got promoted…