The name, Dark Souls II, suggests that this game is a sequel to Dark Souls. Many people mistakenly thought Dark Souls was the sequel to Demon's Souls; the new, obvious relationship in the names certainly seems to require one of them to be related in some manner to the other.
This looks like it may be the result of the Chosen Undead from the first Dark Souls game choosing to become the Dark Lord and ending the Age of Fire, (and killing the Lord of Sunlight) leaving the world colder and bleaker in the aftermath. We are shown a very bleak setting that looks like something between the colorless, grey themes portrayed in Demon's Souls and that of the Age of Ancients in Dark Souls, and a world of absolute Dark.
On a side note, I've noticed several people comment about the masks. Similar white masks are depicted often enough in Japanese manga/anime, often pure white or with a few simple, stylized markings. That being an influence is certainly possible being as this is actually a Japanese-made game, and there are already several other Japanese objects in the series. (katanas, Ciaran's white porcelain mask) Such masks are often used on assassin characters or frightening, unknown characters.
As for the dragon-perhaps the ancient stone dragons have left more modern remnants? Or perhaps the new director simply insisted on traditional western dragons-though I note that there is only ONE depicted in the trailer.
So, what are your thoughts regarding this?