User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-2.50.239.45-20130401061022/@comment-5929284-20130401122410

I doubt Gaea will fully rise. We have a bit of a Kronos situation on our hands- If he had taken his Titan form at full strength the KABOOM, it's all over. The same goes for Gaea- and it's been said multiple times in the series- if she fully wakes, the 7 will lose the battle. My guess is that she will very nearly wake in the 5th book, and that will cause time pressure, but she won't.

Eidolon wise, I personally don't feel like Rick would use the ' they've been possesed and need to fight' plot point again. It would feel a bit stale. Just my opinion though.