The leaked building clearly resembles the walls and battlements encircling Silvermoon:
Both buildings are rectangular in shape, both buildings are elegantly built with marble, both buildings have golden decorations protruding from the wall (the shape of the decorations is different but it can be justified with the usual discrepancy between cinematic and in-game model).
But what does this mean, exactly?
Well, it is actually very simple. I suspect that the Ren'dorei will finally put their plan in motion, as long orchestrated by Alleria Windrunner and Magister Umbric, their plan to bring Quel'Thalas back into the Alliance. Driven to desperation by the power of the Ren'dorei and the Alliance, the Horde will resort once more to enthralling Alexstrasza and forcing her to create Red dragons for war purpose, for the purpose of halting the Alliance invasion. This is also why there is a figure clearly resembling an orc in front of Alexstrasza who could be chained atop the walls of Silvermoon. Let us also not forget that much of Quel'Thalas' forests burned and were incinerated by the Red dragons during the Second War, so we can't expect the Blood elves to have much care for what happens to dragons.
The aid of Alexstrasza and her enslaved dragons will give the weak Horde a fighting chance against the might of the Ren'dorei (led by Alleria) backed by the strength of the Alliance (led by Turalyon).
This will not be a surprise for most of us, who have been expecting a Quel'Thalas revamp in 10.0.
I expect to be proven right about all of my predictions tomorrow.