I have been doing some tumblr research and here I present my findings. Feel free to contribute to my theories in the comments, I will make a video of this debate once I've mulled over it a little more.
We have his tweet and this video as base knowledge:
So here is what we know:
- The three words for the last time were woman, hound and fall. This was easily relatable to Irene Adler and thus The Great Game, The Hounds of Baskervilles and The Final Problem in which the Reichenbach falls were mentioned.
- Moffat stated that anyone with knowledge of the series would be able to guess which episodes the words referred to.
- Mofftiss said that there are still many stories to be told in the Sherlock universe and that season 3 will end with a cliffhanger. Therefore we have fairly strong indications that it will continue for further series.
Possibilities here include the following episodes:
- The Sussex Vampire: this story makes reference to the giant rat of Sumatra, which is quite a clear link to rat.
- The Boscombe Valley Mystery: in this story there is a vague reference to a rat, since a man last words were rat, later found to mean Ballarat.
- The Empty House: According to this website, Gatiss confirmed that season 3 would start with an adaptation of this episode, since it is the next one chronologically, the one where Sherlock comes back.
So here we have it, as far as I can see I bet on the first episode being a combination of The Empty House and The Sussex Vampire for the teaser of rat.
Everyone here seems to be thinking that this is about John and Mary's wedding, but I differ in opinion. If it were John and Mary's wedding, it would be chronologically taken forward a lot and Mofftiss have said that they are looking forward to growing up with the characters as we have met them very young. I doubt that they skip forward so fast therefore I will not consider wedding to refer to this.
Let us consider what other adventures refer to weddings. Now, many adventures mention weddings in passing but here are the ones in which they are central to the story:
- The Noble Bachelor: In this adventure a bride attends a wedding but disappears from the reception so it is a possibility.
- Charles Augusts Milverton: In this adventure a blackmailer breaks engagements for a debutante and therefore a definite possibility.
It has been confirmed by various sources of the internet, that bow is to be pronounced as "take a bow" or "bow to the queen" rather than "bow-tie" or "the bow of a violin" but this has not been confirmed.
Now, a lot of people think it could be a reference to the episode His Last Bow but this is the last adventure in the universe of Sherlock Holmes. Since Mofftiss want to continue and since this is the only episode that I can link to bow, I suppose it will be an adaptation of His Last Bow.
And here concludes my investigation! Tell me what you think in the comments and we can defeat Mofftiss!
DISCLAIMER: I am in no way an expert and have based myself of off many things that I have found all over the internet. I am not asserting which adventures are going to be made into episodes but only giving my humble opinion.