At this point in terms of atonement, we’ll need to see what Blizzard actually has the Horde do. There should be at least something to address the occupation of night elf lands, move that story forward even if it’s not reflected in game. If the Horde doesn’t give back those lands in some capacity, then… well, it would be even worse than MoP.
It would mean that the Horde actually comes out on top and better than before, and will have lost nothing. Because, as per the lore we have now, Sylvanas never actually cared for the Horde and was using them as sacrifices for her own gain. Combined with Thrall coming back, and the addition of the allied races and their lands, the Horde is stronger than ever. Especially when they break out the Blight-killing Macguffin we all know they have up their sleeve and cleanse Undercity.
Really, with this story Blizzard’s kind of forced themselves to do a world revamp in some form.