Well, next year he comes out with Magnus Chase and the Gods of Asgarth. Magnus is Annabeth's cousin, so there's always the possibility that our characters may make a cameo.
In House of Hades, we find out that Nico had a crush on Percy. So, this person is saying that Poseidon, being Percy's dad, is interested in the fact that Nico likes Percy.
I'm home at last! At Camp Half-Blood!