Well I think if 'Nelo Angelo' will come into play in DmC, Vergil is not quite there yet, yes he fallen pretty bad, but really is he that far off dmc3 Vergil, cut himself off from Dante, willing to use demons to get what he wants, not to mention that Vergil didn't mind destroying a good section of a human city in order to retrieve more power.
All I see from this Vergil is that he has cut off two people from his life he sees as what caused him to fail in succeeding in 'his' plan, he may still want to rule the humans to protect them from himself and now sees the demons as a means of an end of getting through the last hurdle to get what he wants, Dante, afterwards he could more than likely dispose of the demons once they have done what he needs of them.