Sadly, this is not true. Berial said ''when I came to this world 2000 years ago, there was no such human as the likes of you''. After that he says ''your arm! You are not human! You are just like he was.'' Berial hadn't been in the human world for 2000 years, so the person he's referring to is Sparda, who rebelled 2000 years ago. Hence why he says ''there was no such human as the likes of you (but there was a demon).
There is all kinds of symbolism in DMC4 that points to Nero being a modern-day Sparda. His story about becoming a demon and trying to hold onto Kyrie is basically Sparda and Eva in reverse (Sparda would sort of become human since he sealed his power in hell when he closed the hell gate).
Vergil doesn't get a new campaign. He's just a new character with which you can play DMC4's missions. There will be two new cutscenes: opening and ending. In those cutscenes, it will be explained what Vergil was doing in Fortuna around a year before DMC3. The DMC4 novel tells this story too, basically. From what we've seen in the teaser trailer, it looks like Vergil conceived Nero with a human woman (considering Nero is so weak and has no real DT).
The character models... I have to say I think they look rather bad. The DT looks pretty good, but for Vergil's regular form, it's like they took textures from the late PS2 era. His face looks pretty mannequin-like, and his hair doesn't seem detailed. But maybe what they showed was just an early render.