User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170307010853/@comment-9595671-20170307024000

Well we already have one bit of info about their older selves that Ex confirmed in the EX novel, all of Issei's harem have big breasts. I think they've all likely become real beauties if that's the case.

Although it does make me wonder if this was a natural result, or if Issei managed to turn his original thought of boosting Rias' boobs (he thought they might get bigger) into reality. If it's the latter... then poor Sona cause she's still flat as Ex also confirmed ^^;

And we have technically seen one character's older self too, Koneko. Her Shirone form is essentially what she'll end up looking like in the future.