Honestly, I hope he isn't playing Khan.
Khan was a minor villain in the original series - a one episode wonder soon forgotten. Much like Nomad.
As awesome as Khan was in the original ST2, his presence in the movie made little sense. Why did both of the original Star Trek films insist on being reboots of fairly lame episodes? They did it to Nomad in ST1, and they did it with Khan in ST2. Not that ST2 wasn't good, but it didn't need baggage of a lame episode. ST3 and 4 managed to be great without relying on ripping off old episodes - as did ST6. (ST5, of course, was a reboot of the episode Roddenberry could never get made - mostly because it was terrible).
Oh, and all of the Next Gen movies - every single one - was terrible. Picard was out of character, everyone else other than Data got screen-time cut down to the minimum, and all the interesting character development in season 7 of TNG (not to mention DS9) got thrown out the window.
... what was I saying? Oh, right - Khan.
Seriously, they can do better on villains. There are some really good ones from the Original Series. Or - shocking idea - what about remaking one of the episodes that didn't HAVE a villain? City of the Edge for Forever? Devil in the Dark?
Balance of Terror? Okay, Balance of Terror has a villain, and they might not want to revisit the Romulans so soon, but... that would be freakin awesome. They could combine it with The Enterprise Incident for a meatier plot.
Or maybe Day of the Dove for some Klingon action?
Seriously, there is way more interesting stuff than Khan. Here's hoping that Cumberbatch gets something other than a frozen mad-man to play.