Vaughn's to good to be bad. Everyone loves him!! And I'd be crushed if I found out he was a bad guy!! REALLY REALLY REALLY CRUSHED!! They'd have to take me to the hospital or an asylum.
I don't that J.J. would make him bad, everyone likes him too much. Plus, it would get way unrealistic if he was killed or was bad even though Sydney's been dealth an extremely unlucky hand; it's not that bad.