User blog comment:Mnzombie/Issei's Peerage/@comment-5172218-20120617193003/@comment-16075832-20130708224635

I don't think it was ever confirmed that Rias would become Issei's Queen.

You're right about one thing though, Issei will always be Rias's Pawn so even if he becomes a King, as a reincarnated devil, he'll have to participate in the rating games that Rias' participates in as her Pawn. I think Ravel explained this to him.

Also, Issei promised Asia and him would always be together and Xenovia stated in Volume 6 that she wished to join him as well.