@M.LeMarchand said:

"Death on the Nile" took place in 1937 and its epilogue showed Poirot making a fairly major change to his life. This one is set in '47 and, while he has made other changes, the change he made in '37 has now been reverted. Will we ever find out why?

This is Kenneth Branagh's retcon of Hercules Poirot, so it is anyone's guess. For example, he discovered that it was not 'the little grey cells' that helped him solve cases, but his moustache. Or simply that having a moustache made him more attractive to women, as Salome told him that she missed his moustache.

Or did Branagh think "Death" would be his last turn as the Belgian detective and so he could make changes to the character without needing to consider future productions?

There are plans for a fourth and more movies in this franchise, "If Ken wants to do more, and Michael wants to write more, we'll certainly do another. There's a lot of material still to go, so we're not going to run out of inspiration.".

@wonder2wonder said:

This is Kenneth Branagh's retcon of Hercules Poirot, so it is anyone's guess. For example, he discovered that it was not 'the little grey cells' that helped him solve cases, but his moustache.

Love this theory!

@wonder2wonder said:

There are plans for a fourth and more movies in this franchise, "If Ken wants to do more, and Michael wants to write more, we'll certainly do another. There's a lot of material still to go, so we're not going to run out of inspiration.".

I can't see them even getting close to David Suchet's run, which did include "Roger Ackroyd". The article is technically correct in that it was an "episode" rather than a "film" but by then the eps were feature length.