This sees the appearance of John Hurt as the missing Doctor - as the eleventh Doctor (or is it twelfth?) states:
I've had many faces; many lives. There's one life I've tried very hard to forget.
That's OK, Doc - the rest of us try just as hard to forget the sixth Doctor.
Let's have a look at the trailer and consider what it could be (all images are (C) BBC)
Dalek flying saucers of the design we have seen from Bad Wolf/The Parting Of The Ways and the planet looks likes Gallifrey - seen in The Sound of Drums/The Last of the Time Lords, The End of Time and The Name of the Doctor. We are clearly in the Time War here, that time-locked Time War.
And the Capitol on Gallifrey.
Standard familiar older-paradigm Dalek, of the main design from Dalek through to The Stolen Earth/Journey's End and also seen to a lesser extent in Victory of the Daleks and Asylum of the Daleks. Just a thought on the last of these - the opening scene was on Skaro, which had been destroyed by the Hand of Omega in Remembrance of the Daleks. Perhaps the Time War rewrote some of the Dalek history and undid the destruction of Skaro. These are not the Remembrance-Daleks.
Maybe I need new glasses (actually, that reminds me, I do need to buy new glasses - have the prescription in a folder somewhere) but when I first looked at that my thought was "Sontaran". Yet in The Sontaran Stratagem/The Poison Sky, Staal said that they were not allowed to fight in the Time War.
The war isn't going all the Daleks' own way.
This reminds me of Star Wars, but the desert planet could be the Gallifreyan wastelands that Leela was exiled to in The Invasion of Time.
My first thought was of Obi Wan Kenobi, to be honest.
The tenth Doctor is saying "You've certainly come to the right place". In the trailer, the words immediately before that is the missing Doctor saying "I'm looking for the Doctor". But this could just be the way the trailer is edited - and raises the question of why the missing Doctor would be looking for himself, unless somehow he was made aware that his later self/selves (but note he says "Doctor", not "Doctors") were around.
The tenth and eleventh Doctors look a bit disgusted at finding their earlier self.
The Virgin* Queen running through woods from something - maybe the same woods we see the tenth and eleventh Doctors in.
[* Assuming this is before The End of Time]
And our first sight of a Zygon.
An explosion of some sort - clothes look modern, some white coats. UNIT's scientific section? Is that Kate Lethbridge-Stewart in the middle?
Now, this is incredibly interesting. Up till now, we could assume the Time War was something being looked back at. But surely this is the three Doctors together. And look where they are - doesn't it look similar to where the Dalek on fire was in the fifth picture?
[With a second glance, seeing the lamp and cart, I now say it doesn't]
Although in its emergency temporal shift at the end of Daleks in Manhattan/Evolution of the Daleks, Dalek Caan ended up within the Time War itself, and was able to change events (e.g. undo Davros' destruction when his ship flew into the jaws of the Nightmare Child in the first year of the War), in The End of Time a major part of the plot is that the War is time-locked (by who? or by what?) and Rassilon's plan involves ensuring there is one path out of the time-lock - via the sound of drums in the Master's mind. Surely near the end of that, the tenth Doctor and the Master managed to time-lock the War again (at the cost of the Master's life?).
If the tenth and eleventh Doctors are able to enter the Time War, then there must be a way past the time-lock. Maybe accidentally, a la Dalek Caan, or deliberately. The Doctor has more control over the TARDIS now, so unlikely to be there by accident. To get past the time-lock, he needs a connection with something in the War - and surely, the eleventh Doctor and Clara Oswald entering his timestream in The Name of the Doctor, they have found a connection and can go into the War. After all, there are parts of the Doctor's timestream which lie inside the War.
So, the Doctors enter the Time War - and maybe, like Dalek Caan, they change it in some way. What could this lead to? A return of the Time Lords? A return of the Master - but if he was only evil because of the sound of drums in his head, which is a product of the Time War, would a resurrected Master be a different character totally?
A Doctor riding out of the TARDIS - did Arthur continue to travel in the TARDIS after The Girl in the Fireplace?
The eleventh Doctor falling over what looks like modern-day London.
A Zygon smashing what is presumably glass.
The lady vanishes - Clara has managed to get hold of a vortex manipulator similar to those Jack Harkness and River Song have.
The missing Doctor has come across something....
... and Rose says (is that the missing Doctor she's addressing?) "The Moment is coming".
Does this mean the red crystal-like thing is The Moment - after all, in The End of Time it was stated that the Doctor had The Moment and might use it to destroy Dalek and Time Lord alike.
When I watched Bad Wolf/The Parting Of The Ways, I assumed that - just as the Doctor was preparing a delta wave to destroy the Daleks, but had no time to perfect it, so it would destroy the humans on Earth as well - that he had destroyed the Daleks and Time Lords with the same thing. But it is clear later that it was Gallifrey that was destroyed. Why do that?
In The Stolen Earth/Journey's End, Martha Jones is in possession of the Osterhagen Key, which can be used to destroy the Earth. As she explains to the Daleks - they need the 27 stolen planets for something (the Reality Bomb), so what if they just had 26?
Is this something here? Why destroy Gallifrey at all? Why respond to the Dalek invasion of Gallifrey this way? What was there that should not fall into Dalek hands? Not time-travel - they have that, so would have no need for the Eye of Harmony, or the Sash of Rassilon. I doubt that regeneration would be of use to the Daleks. If Gallifrey were similar to Earth, then it could form part of the plans for a Reality Bomb, but this was Davros' scheme and by the time the Time War was coming to a close he was already dead (but this was overturned by Dalek Caan).
The only thing I can think of is the Hand of Omega from Remembrance of the Daleks, which I believe returned to Gallifrey.
In a fortnight's time, all this will fall into place.