I have a feeling he might be working with the people who have Dante chained up or whatnot.
At the end of the trailer, when Dante leaps off the wall when he falls. You see sumone falling after him (its hard to see, but its there). Which kinda fits, because in the scene where you hear the voiceover say "My name is Dante" it looks like Dante is looking at sumone while he puts his guns away (and of course Dante falls off the roof to escape whatever is going after him). It might be Vergil whose the one going after him to bring him back to that asylum/jail or whatever.