Whilst I really like the idea of this being a sequel to SOTN - thus making a Dracula X trilogy - it's also possible that the trailer is the first of several for the 1999 game.
Perhaps they're initially releasing "character" trailers, with brief descriptions of the various individuals who take part in the battle. They could have started with Alucard because he's the most easily recognisable (the others would be Julius, probably a Belnades, possibly Mina's father, and probably Saint Germain).