Considering that the new big bad guys represent The Void(shadow), much will have to changeWe don't know if prophet Velen's vision is going to happen. His whole arc in legion was about forging his own path instead of depending on "the hand of fate". Xe'ra's prophecy about Illidan also didn't come to fruition, and Xe'ra was a prime naaru. What has been alluded to in both the game and other media like the audiobooks, is that both light and shadow have the power of foresight, but while the light sees only one path, the shadow sees all paths. Velen's visions come from his closeness to the Light, it isn't surprising that it was a vision of mortals fighting to defend it. The Light is granting him that vision in its own self interest. As we've seen from Xe'ra, and I think we will continue to see, the light and shadow are not a binary of good and evil. Being with the light doesn't necessarily make you good, nor being with the shadow necessarily makes you evil. I definitely think there's more to it than just ending up in the army of the light as the good guys against the shadow. But that's just my opinion.