The rumor is out that movie number two will introduce Khan - possibly Kirk's greatest nemesis.
This cannot be "The Wrath of Khan," though.
See TOS episode "Space Seed," as Kirk has never met Khan yet (in this timeline).
The crew needs to discover The Botany Bay or someplace else where genetically engineered "augments" are being kept in stasis-sleep.
This could be cool. Note: Khan probably has to live through the end of the movie - and somehow escape death. That way they can bring him back for another movie.