User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-68.51.98.95-20121121230902/@comment-3146930-20121121231840

Kronos was pretty much destroyed at the end of The Last Olympian. He tried to revive using Luke as a stepping stone (calling his body up from the pit and into Luke). When Luke killed himself, Kronos was scattered to the winds and didn't return to Tartarus (as he isn't a monster). If they do see him, it would only be the body and not the mind.