11/10/2013 07:14 PMYou are from universe A, going to parallel universe B 30 years ago. Anything happen in universe B won't affect history of universe A.
Posted by Mokgath
Right. Garrosh goes back to Draenor and starts messing with things to make his perfect Horde which creates an alternate timeline. From that alternate timeline they find a way to come through the Dark Portal to our present. A very real danger to our current Azeroth, but changes on the alternate timeline's past would not affect our present (except for the angry murder-orcs spilling out of the Dark Portal).
As Dave said it's not something you need to worry about, this isn't the time travel/paradox expansion; it's about exploring that setting, visiting those locations, meeting or facing these legendary names and figures from the past, and experiencing some extremely important settings of Warcraft's history in a bigger way than we've ever done before.