There’s something knocking on the back of my mind… from last week’s episode, Moffat seemed to point that Missy is Clara (the “I don’t like to be called Miss” line makes me think that Missy could be a future version of Clara that is trying to safe the Doctor from a darker path, the one he’s going through now).
On the other hand, Dannys relationship with the Doctor is quite antagonist (he seems to be trying to separate Clara from the Doctor, and it doesn’t feel that Clara’s safety is his main reason). Could Danny be The Master (and Clara The Misstress/Missy). All in all, Orson Pink said that “timetravelling was a family think”, but didn’t state which of their grandfathers was the time traveller, so they could be both.