If were following the Night Elf/Blood Elf themes here. I think the two most likely cities are going to be Silvermoon and Darnassus. Not sure if this is going to happen though, cause they said that they weren't going to do anything "cataclysm-esque".
In reality, it probably means that Suramar will be the city that will be burned.
I don't see them doing Org again in any case.