I realize that it's part of the fun of being a fan--I do it myself, constantly

--but I think a lot of people are overthinking this.
I don't pretend to have the slightest clue what Moffat's going to pull out of his hat, but I know this:
Moffat, while very much a Doctor Who fanboy from back in the day, is also a professional storyteller. And I guarantee, he's well aware of the requirements of a TV program and audience.
In other words, the solution to what's going on is
not going to require the sort of in-depth knowledge of Dr. Who history that many fans are delving into. It's going to draw on the mythology introduced in the
modern series (Eccleston and onward), and/or on information that can be
clearly and succinctly communicated in the course of the single remaining episode of the season.
And no more. There's absolutely no way he's going to start pulling out obscure characters/historical details that will leave half the audience scratching their heads and wondering where the hell that came from.
If a theory as to what's happening next episodes
requires that the viewer be a die-hard fan of the
older Doctor Who series in order to undestand, than I can all but guarantee that theory's wrong.
