The threat of humans/nephalem has been a thing since before the Sin War (just like the in-fighting between evils) when the Angiris Council voted whether to eliminate them, so this is not new at all. If you listen to Zoltun Kulle in Act 2, he tells you how Tyrael prevented that from happening by being the deciding vote. This was after the whole Uldyssian storyline.

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As for hell winning, as per the scroll of fate, **hell does win when humans aren't involved** but says nothing about the other outcome. You can read more about that and Itherael here: http://diablo.wikia.com/wiki/Itherael

Either way, this particular story is wrapped up. The real questions are whether they expand on the realms of fate as they relate to the prophecy with another storyline altogether OR go back and do something prequel style. I don't think the blood shards are anything significant lore-wise at all.