User blog comment:Swordbirth18/Possibilities for highschool dxd season 4/@comment-26527700-20150823023052

I don't see how they could ever goback and do the Rias Sona RG. Rose has already joined, Tsubaki's SG has been revealed, and Sagi's SG has been upgraded. Any RG featured would be so different to the point of not resembling the LN at all. All of the abilities that debuted during the RG in the LN were featured in the Loki battle. Given all of that, there's really not much point.

On the flip side, given what they did with BorN, I wouldn't be surprised to see them really mess around with Season 4. They could potentially cover volumes 9 and 10 in only 6 or 7 episodes and spend the rest covering up through volume 12. Not saying they'd definitely do that, but it certainly isn't impossible.