User blog comment:SonOfZeus1200/The Camp Half-Blood & Kane Chronicles Series will collide!/@comment-112.202.96.33-20120504133501/@comment-3146930-20120504210400

Rick mentioned it awhile ago at a Question and Answer session. When asked if the HoO would have another sequel, he said he wasn't sure and he was planning on possibly writing a Norse series. Then a news article came out last year revealing he was going to write it.