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Seriously though, how do you know that?
Now let me see...there is literally no evidence to suggest Cumberbatch is playing Khan. He's English, he doesn't look anything like him, he's a member of Starfleet and he seems to have some sort of connection to Robert April. A few red herrings on websites isn't any sort of proof. Abrams and co. aren't idiots, they know the expectations fans have and that they're heavily debating everything.
Everything related to Khan is pure assumption, even the claims that Paramount and Abrams can't keep the villains identity under wraps. The fact is most of you want it to be Khan so much, you're willing to overlook the plain facts, which is a classic example of clutching at straws. I've therefore deduced after looking at all the evidence, that Cumberbatch isn't Khan.