User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-68.11.161.173-20130404000409

I think that

1. Nico will sacrifice himself so Percy and Annabeth. An oath to keep with a final breath.

2. Reyna will betray the Romans and join the Argo 2 crew, where Leo falls for her.

3. That Nico won't have a POV.