Could Shona be 'The Magician's Apprentice' that the Series 9 premiere title is alluding to? It would certainly make sense, going from the evidence in Last Christmas. She was taking notes throughout the episode and even called the Doctor a magician at one point. Coincidence ? Maybe. Maybe not. Doctor Who fans are notorious for reading into things but they can be excused in this case. As always, only time will tell. But it would be seriously annoying if the identity of 'Dave' was never revealed. Shona has seemingly let the past go but the fans would be far less forgiving.