If he is the leader of the Order. He will remain the leader for a very long time. It's what he built, in truth it's a small army that he's trying to expand. I'd love cameo appearances or name drops of pursued demon hunters. You know, the famous ones that we all know and love.
To me, Vergil is the best character in the DMC series. He sets a goal and he goes for it not stopping for anyone to reach it. The goal he chose was power and it's not to take over the world, it's to protect the things that he loves. Dante understands that, which is why he mourned for him. Thing is, Vergil didn't limit himself to just killing demons, he would murder ANYONE who stands in his way. The tower itself being a huge "Screw You." To the human race. What if, Vergil was not only fighting for power but for Nero and Dante? I like to believe so.
I'd like to mention that in MvC 3, Vergil shows mercy to his foes and tells them to "Stay out of his way." I can't remember anything else at the moment, but you guys get the geist.