I think that they'll most likely get a "big name" actress to play Hippolyta. That seems to be what CBM's do, cast relative unknowns in the main role, and then surround them with more high-profile actors. Given that Patty Jenkins is directing this, my first thought went to Charlize Theron. She's proven that she can play "queen" characters before. I still offer up Cate Blanchett as a possibility as well.