The scariest thing about the pjo series is, prophecies are more definante then we often think. The great prophecy, of Olympus razed and the war, only stated it belonged to a sixteen year old demigod of the big three. It didn’t mention a name. Not a gender. Just a child and a choice. If we go by timeline, the character who should have gotten this was Hazel. However when she died at thirteen, Bianca took it on a few short years later. Then Zeus tried to destroy her, succeeded the second time and it went to Thalia. The point is that in order Hazel, Bianca, Nico, and Thalia didn’t just circumnavigate their fates, leaving Percy and Jason to bear it. Prophecies do not discriminate. They come to pass with any hero, anywhere, at anytime. The kids were all just insurance policies for the earlier heroes.
Which brings us to this: the seven are just described as the seven. The only, ONLY case of name-dropping seen was Nico (angel’s breathe) occurs here, but he could easily be part of a different group of demigods later, being one of the youngest kids in the group. Annabeth has other siblings (wisom’s daughter walks alone). Zeus can have more children, and so can Hephaestus. It does not have to be this particular group.
So what if its not?
What if they do fall, and go back to the doors of death? What if the series continues, with another seven?