User blog comment:B214/Don't ask about season 4/@comment-86.199.208.148-20160703232037/@comment-28730380-20160704012852

The LN for DxD is far ahead of the anime and the manga is far behind. From what i know of, the anime seems like it follows the same general story line of the LN but several areas are moddified. From the rumors that i've seen, Season 4 is supposed to have Rias and Issei's children from the future which is never spoken of in the LN. I could be wrong here as i only read up to volume 15 and it could be something in a further on volume. In that case, they are not following the order of events according the the original storyline from the LN.

For manga, they seem to have stopped making them for a while, it has been months since they released a manga

For the LN, you could go to baka tsuki and read the translated version, there is also a app if your interested.

From what i know, the popularity of DxD has grown and i don't think they would randomly stop making the series, its a great source of income. Season 4 will probably come out, im predicting this summer or possibly sometime in september. (80% sure)