Will there be a 4th episode of Sherlock on Sunday 22nd January?

Spoilers for Season 4, Episode 3 of Sherlock.

There is a theory floating around the internet that there is a secret 4th episode of Sherlock, which will air on Sunday, 22nd January.

I love interesting theories, so here are the main arguments (collected from around the web) that there will be a 4th episode:

• There is a TV schedule which shows a 4th episode. (looks fake to me!)
  

• Sherlock commented in Season 4, Episode 2 that people stop looking at 3. There was a fourth recording device, so why not a fourth episode?

• The date on Sunday is 22/1 (UK date format) ‘221’ is the address of the Baker Street boys.

• The TFP was emotional, less logical, because it takes place inside John’s head. John was actually shot by Eurus. If true, this would need to be resolved in a 4th episode.

• The Piccadilly circus board in London has been turned off for renovations. There will be a temporary advertising banner. Some say that this will be Moriarty’s ‘Miss me,’ indicating that he will return on Sunday.

• Amanda Abbington (who plays Mary) said:
  (Sherlock Season 4 Extra bits) Some fans have taken ‘If we can pull this off, then it’s amazing,’ to mean that the writers are trying to pull off a secret 4th episode.

• Sue Vertue, the producer, said in 2014 that: Sherlock might not always have 3 episodes per series

• The security footage of Eurus shows EGY followed by the number 18992201 in the corner. Is EGY code for a new episode name, and 2201 Sunday’s date?
  The 1899 could refer to a 4 act Sherlock Holmes play, that was first performed in 1899. The key thing being 4 acts, a hint to 4 episodes.

  

  EGY 18992201

Moffat has denied rumours of a secret 4^th episode though: Moffat on 4th Sherlock episode
But then, if it were true, he would, wouldn’t he?

Do I believe there will be a 4th episode?

It seems unlikely, but it would be cool if it were true, and we got a further episode with Moriarty. I will never say no to more of my favourite shows!

I loved The Final Problem. Perhaps it was intended as a final episode. Maybe they wanted to tie off this arc nicely? The lack of cliffhanger seems wrong though: we have not come to expect such a happy ending from the series.

Whether all this speculation turns out to be true or not, it is interesting to watch the theories unfold. I will watch BBC1 on Sunday night just in case, because you never know! (Actually, I’ll be watching Apple Tree Yard, because it looks good!)