User blog comment:SonOfZeus1200/The Camp Half-Blood & Kane Chronicles Series will collide!/@comment-5112532-20120526092417

I highly doubt that this is going to happen as it would be just soo confusing, I mean he's already crossing the Roman gods with the Greek ones, and its the gods just taking diffrerent forms.

And on his FAQ page (http://rickriordan.com/about-rick/faq.aspx) he says:

Q. Would you ever do a crossover series with Kane characters and Percy Jackson characters?
A. I don't know. Yes, the worlds exist side-by-side. You've probably noticed some 'shout-outs' to the Percy Jackson series within the Kane Chronicles. I think it would be pretty confusing to mash the two series together, though! It's tough enough keeping one set of gods straight. Two might be hard. If I ever wrote a book like that, it would be quite some time from now. Remember, each book takes one year to write, and I've got a lot of other books to write first.