Well, nothing so far is hinting towards any kind of “WoW plot changes”. The changes to the story are most likely going to be just a few added dialogue lines and changing the detail of the maps’ layouts (and my guess is the Culling map is one of the drastically changed map, other maps will get a lot minor changes).
Edit:
Note, that the unofficial survey is up! I added the link on the OP, but I’ll add it here too, just in case.