I've been thinking about the whole theme of Dark Souls 3. It centres around the 'decay' of every thing, every process of nature that goes on in the game and has been going on since DKS 1.
It gives us a huge hint that Miyazaki himself didn't want to do this game, but was pressured by From Software to make it, owing to fan's obssession with DKS 1, 2 and what not.
Everybody was already expecting a Dark Souls 3 to follow up to DKS 1 by early-mid 2015.
So my expectation from this DLC won't be much, it'll just be a wrap-up to the previous DLC's story and will give us another hint or two about what the Dark/Deep is, and how it is involved in the decay of natural processes. It will most likely feel like Miyazaki just wanted to be done with this damn game and then get working on his current interest.
The whole 'flame is dying out' thing is from software trying to tell us that their own interest in this series is dying out/dead.
It might also tell us why there are so many hollows in one particular place ( Londor I guess, going by the 'city of the dead' thing).