When it comes to iconic villains in Star Trek movies, there's none more memorable than the late Ricardo Montalban's Khan. In a recent interview with MTV, Star Trek director J.J. Abrams didn't say for sure whether Khan would appear in Star Trek 2, but he also didn't rule out the possibility.
Dealing with Khan would certainly be a challenge, but we had an equal challenge in finding our crew of the Enterprise. While I don't want to approach the second film as a remake of episodes we've seen in the past, and, you know, I don't think any of the other writers and producers are interested in just rehashing, or throwing characters in for the sake of it, and Khan is certainly the most obvious one in the history of the series for me.... Nothing is off limits in terms of what we're discussing.
Star Trek screenwriter Roberto Orci has said that Khan's chances to appear in the sequel are about "50/50." Javier Bardem could be he front runner for the role should it be written into the sequel.