Also it might be some character who is not released yet.
That would be rather annoying if it was true. Having to buy a $50 boxset just to get one exclusive unit. I mean its okay with the smaller sets like the Light, Dark, or Black Sun sets as those cost were little more then one of the bigger models or around two models. Heck I might be tempted if they have a new re-sculpt of DC and Ayl. But I doubt they would screw their small fan base with such a move.
Plus any new Sameal unit would be natural to be released as a single alongside the boxset to capitalize on interest in the organization. Which is why I'm thinking Sarah might be released after Wolfgang to go with the Church release or Juliette sneaks in before both of them to go along with the Azur Alliance release with Anna Never.
Now I do believe there was talk of another death spirit joining the ranks of Samael so I figure they should be announcing an new unit next month or so.