User blog comment:HollowAvarice/The Seven Half-Bloods/@comment-3459279-20110402214810

I definately agree that Percy will probably be part of the group. I also agree with 2 more Roman kids joining the seven. The last one is tricky and I think they are going to answer it in one of two ways. A) they are going to bring back someone (possibly via the Lotus Casino) who had served as an intermediary between the two camps, possibly because of their dissapearance the civil war started in the first place, and that person will serve as the seventh.

the other option (B) is that a child of Hades/Pluto will serve as the last one. Hades/Pluto has always been the odd God out in the past, and his children have also kind of been treated that way up until the Percy Ultimatun (What I call the deal Percy made with the Gods).

But I guess we will have to painfully wait until the next set of books to come out before we find out.