6. The Doctor Steals Lives From Another Time Lord
We were promised a dark direction. The Time Lords are back (sort of, pocket universe again). Could it happen? It wouldn't even have to be the Master. It would be fascinating for Moffat to introduce a new one, Corsair-style, or it would be the perfect return for the Rani. Imagine it; one of the Time Lords falls through the pocket universe, and the Doctor pounces, stealing their remaining lives. Perhaps that's what all these monsters are here to prevent perhaps this will be the dark corner that the Doctor eventually turn before regenerating into Malcolm 'f**kity-bye' Tucker. Or maybe Susan's still out there, waiting to hand her lives over to him. Now
that would be a fine idea, though it begs a question: if Susan, or another Time Lord could give their lives and prolong the Doctor's life beyond thirteen incarnations, why didn't River's sacrifice?