6. John Harrison Returns
Prior to the release of Into Darkness, Lindelof stated that "If he survives this movie, I think we would be incredibly stupid to not see him again", and given that we now know that Harrison - aka Khan -
does survive the events of the film, there's a very strong chance he'll be rearing his head again in Trek 3. The film ends with Khan being put back into stasis, practically teasing his return for a later film, and though bringing him back so soon might risk repetition, getting to see an entire film with Khan - rather than needlessly obscuring his identity for 50% of it - would certainly be a joy to watch. Cumberbatch was by far the best thing about Into Darkness, and it's easy to imagine how the film could have been far less intriguing without him playing the villain with such delicious vigour. As such, bringing him back for the next outing would be a smart move, as long as his method followed along a starkly radical, different trajectory.