Aaah, how I remember good ol'Night Warriors on the SEGA Saturn!
It's interesting because I do beleive that one of Capcom's headhonchos made the claim that converting these titles to 2D/3D style would be hard to do, since the Darkstalker characters undergo several transformations and such aren't too easy to with SF IV's engine... or so I've been told.
Still, if they go for classic 2D, they need to take a good long look at Skullgirls because that's how you should do a revamped 2D Darkstalkers game.