WoW insider here.

The final boss of WoW is going to be Sargeras. "The Last Titan" it's literally in the title. The players fight him with the help of Xal'atath and after they finally defeat him, there's a cutscene where the world becomes wireframe similar to the final level of Conker's Bad Fur Day. Then Chris Metzen's disembodied face and hands a la Andross in Star Fox 64 appears and we have to use Skyriding to defeat him by using our extra action buttons to shoot B-bombs into his open mouth once he opens it. This is specifically why we introduced the CVar ActionCam back in Legion. After you defeat Metzen he unmakes reality and kills everyone except for himself.
Then the servers shut down forever.