Hey hey hey, back earlier then expected
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So since I was right about dragon isles being 10.0 back during SL beta. I'm most likely right about 11.0.
Chances are that MU murozond and the infinite flight could be the ultimate antagonists of Dragonflight.
Why? Well because Yrel being stuck in AU draenor with no means of transportation here. She's being groomed to be a light aligned antagonist. She could also potentially push Turalyon over the edge, as the B plot of Dragonflight will most likely deal with him and Calia.
So yeah, Murozond will be the final boss, well defeat him and he'll then summon Yrel and the light bound as a last ditch effort against the void. Then boom, 11.0 is set up.