User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-86.176.125.14-20121228212435/@comment-4902593-20121230100637

Of course the very last chapter of the last book will be from Percy's POV. Afterall, Rick has been writing about him more than anyone else for the past 8 years. Plus the  character is pretty special to him since its based on his son Haley. So yes 99% sure.