User blog comment:B214/Volume 23 discussion blog/@comment-77.188.241.163-20170918105018/@comment-31137559-20170923050312

Well technically you can say Asia and Xenovia were Issei's servants since they first appeared in the series and that Rias was saving them for Issei as he wasn't a high-class devil yet but whatever.

Ishibumi did say in the Volume 22 Afterword that some of Issei's future servants would be introduced and that the search for new peerage members is a main theme of this last arc. And I expect we'll see his queen in this arc. Issei's queen is too important to not show in this final arc. We are talking about his right-hand man, his lieutenant, most likely his most powerful servant, and much more. If we only get one of Issei's new peerage members, it'll be his queen.