Keranos has been, historically, the highest priced of the Gods. It seemed the natural first God to start the post-Standard ascent. It's also from Journey into Nyx, which had a very limited print run.
This saw $15 in it's heydey in Standard. You can expect an easy $15 apiece on the back on Eternal (i.e. Vintage, Legacy, Modern and Commander) demand within a year.
Foils are prohibitive to buy in with, at $60-$70 apiece. But I can see these at $150 apiece in few years. I'm not too worried about God reprints, though.
These recently rotated out of Standard, so they've seen the lowest price we can expect until it sees a reprint, if ever.
I think this is a low-risk, medium-to-long-term, medium-yield spec. Not the flashiest speculation, but the sky is the limit on this card, could be $30 within a few years.