User blog comment:B214/General Discussion/@comment-29963364-20161007032244/@comment-9595671-20161008024255

I'd say it's more likely Vali will take the spot of Lucifer while Issei won't take any Satan position at all. There are two reasons I think this will be the case for Issei atleast.

One, the EX timeline heavily implies Issei didn't take the position. Secondly, the Satans can't have harems, not sure the exact reason but B214 said it had to do with how it could effect standings and rankings for houses if multiple people could marry a Satan.

Since Issei's dream is to have a harem, I don't think he's gonna go that path. (Plus it's odd Zekram conveniently didn't mention that when he already seems kinda shady) Plus he'll likely be too bust running ExE in the future.