Well, -Sorian-'s blog entry suggests, that the AI can indeed pick the new Demigods, even if you can't.
thats a bit stupid.... AI cant give feedback...
Well, it's not about just the AI. Once patch 1.2 is out, you'll generally be able to play against the new Demigods, be it against the AI or against human players who may use them (only Stardock members in the Beginning, then some RTP users and then all users).