IIRC, Abrams PROMISED us there would be no Khan in this movie. What good are you if you have to lie to people to get them to see your movie?
Abrams didn't. Simon Pegg and Alice Eve both denied Cumberbatch's character was Khan, and Cumberbatch himself made a comment which was open to interpretation ("I'm tired of having to deny I'm playing Khan"). But Abrams and his minions never promised Khan wouldn't be involved. Indeed, it was one of his minions who first spilled that John Harrison was an alias. But also, when Karl Urban said Cumberbatch was Gary Mitchell, Orci wasted no time debunking that.