User blog comment:Aizen.sama/Are Espadas, Vasto Lorde(s)?/@comment-452405-20100419055753

I doubt Wonderweiss was a Vasto Lorde, there's so few of them apparently so I doubt Aizen would experiment on them.

And like you guys said, this discussion has been around for quite a bit and nothing has been confirmed either so we won't know until either Aizen or Gin say anything.