User blog comment:B214/Light Novel Volume 16 spoilers/@comment-162.202.198.72-20131019091326/@comment-5185939-20131019151103

If the position wasn't already going to be taken, I'd almost bet that Le Fey would become one of Issei's Bishops.

Of course, since Rias will have a free Bishop because of it, it's still possible she'll become one.