I think that Stratholme will become a city, while Undercity becomes the raid. Many people have been speculating the Sylvanis is becoming more and more like the Lich King. The return of the legion it may cause her to snap and fall under the control of Kil'Jaden and then we have to kill her. This would give the Forsaken a new capital city in Stratholme, which was the larges city that wasn't actually a capital city back before Arthas sacked the city.