User blog comment:B214/Talk About What You Want! 3/@comment-16281343-20150101173206/@comment-1359322-20150101175647

Yeah just read his blog. Ishibumi will do volumes focusing on the first four heroines, and then the later ones which Jop mentioned. This is all known.

For Slash Dog, Ishibumi will focus on the secrets of the Japanese myth starting from the Five Great Families, so i guess Ishibumi purposely avoided the Japanese myth in DxD from the start.

Ishibumi also mention some interest in starting a third series that also takes place in the DxD-verse. Though that's only planning, and he needs to see if his health can withstand it.