I don't think it will be Khan. But this...
If my instinct is right and this is going to be about Captain Kirk's mistakes, it could be a culmination of several missions that come back to bite him.
... is something I really
like the sound of. The implication of lots of missions between ST09 and this, possibly even getting to see
some of those missions, and the culmination of that building to John Harrison, the villain, taking on the Federation.