User blog comment:Ixarising/Speculations, theories and predictions/@comment-26821288-20160511202425/@comment-24.113.252.213-20160512012347

I also think that the theory presented by  " 兵藤 一誠" is a valid one, and might even be what Ishebumi uses to explain away the changes he made to the plot of Season 3 (BorN).

I'll bet, during the "bath scene" from vol. 10, Rias will flash back to that "beach scene" in order to make the connection between Season 3 and the (potential) Season 4.