That's not necessarily streaming, that is you loading assets of a zone when you enter it. You can see that happen all the time with fast connections too becaus

That's not necessarily streaming, that is you loading assets of a zone when you enter it. You can see that happen all the time with fast connections too because their flying mounts move faster than their location reference. WoW does stream some assets though. When a large patch goes in you can't play until specific required files are in (most likely the maps and models) but it will let you play while it continues to fetch all the high-end textures.