Thanks to the production panel at the Convention we know that Episode 1 features the Daleks. Not just the recent dayglo plasticky Recycling Bin versions (I am so not a fan) but lots of older models from the 60's and 70's. This isn't a spoiler, as the following image was tweeted by Mr Moffat himself.
That's a 60's one. If the dome is black under that dust, it's one of the Emperor's retinue from Evil of the Daleks. Other images appear to show the gunmetal grey version from Genesis of the Daleks. A new Dalek's eye stalk emerges from the snow in the trailer (filmed in the Sierra Nevada mountains of Spain whilst they were working on Episode 3). I think it can be safely assumed the episode is written by Steven Moffat. It will be interesting to see how these Daleks from different eras fit into the plot.
Episode 2 is written by Chris Chibnall and appears to be set either in Ancient Egypt, or a Stargate type alien world.
This one features Rupert Graves (Sherlock's Lestrade) and Mark Williams of Fast Show and Harry Potter fame. The trailer also features another HP actor - David Bradley - acting villainous. There are also some large yellow robots.
Episode 3 is Toby Whithouse's wild west adventure, which features Ben Browder, late of Farscape and Stargate, and the marvellous Adrian Scarborough (Psychoville).
There is some kind of cyborg gunslinger in the trailer - shades of Westworld.
Episode 4 we know next to nothing about, but episode 5 will see the departure of Amy and Rory, in a story set in New York (filming there later this month) and it features the Weeping Angels.
The order of episodes is always subject to change naturally. There will be 5 episodes this side of Christmas. The sixth story will be the Christmas Special itself, which introduces the new companion. That leaves 8 episodes for the New Year, one of which is written by the annoyingly brilliant and versatile Mark Gatiss.
Roll on the Autumn.