User blog comment:Swordbirth18/Possibilities for highschool dxd season 4/@comment-26709288-20150922132132/@comment-26709288-20150922150607

Well eventually the fallen angels could have a system of reincarnating members. I don't believe they would allow angels and devils to grow in numbers but stay behind even with their being peace among the three races.

Also on that episode the others had questioned him about it saying "how can that be? You became a fallen angel by falling?"

And his reply was "It's just a suggestion" which made it seem like he was hinting along that line.