User blog comment:Jopjopjop/Volume 20 Spoilers/@comment-72.148.177.121-20150727223553/@comment-24502975-20150728173610

We're definitely getting a 5th arc. Shiva arc has been teased since v13, as an extra chapter/finale to the story. Especially since Ishibumi (allegedly) said that Ise won't get any more power-ups, I completely agree with @92.40 in that the last arc will be more focused on other forms of growth (high class Devil/peerage, final harem stuff, actually completing the harem etc.)

Besides, in v20's Afterword it certainly didn't seem like he'd stop DxD before he ran out of ideas...