User blog comment:Cookievalenzuela666/which girl is going to get their own volume next?/@comment-79.130.69.4-20140908134740/@comment-1359322-20140908155744

Volume 19 - Xenovia

Volume 20 - Vali Team (this seems most probable right now since Ishibumi already mentioned his intention on doing this)

Volume 21 - Sona & Tsubaki perhaps, it'll be a good way to show Tsubaki's BB.