Well they've stated that EVERYONE will see the changes to the old world zone, if they buy the expansion or not, so you just cant be a Blood elf, Draenei, Worgen, or Goblin, cant go to their starting zones either, and cant be a DK, cant go to outland, northrend, or the new 78-85 zones. Only confusion I would see is a new player with a vanilla, or old school battlechest wouldnt be able to make a worgen/goblin, but that's about it.