I don't think Isaac is still is part of a gestalt mind, but something happened to Isaac. The link basically formed a gestalt mind. When some of the GM's croaked, they would have experienced the same sort of transcendental state that Bunny experienced when she croaked. (Remember all of the things she suddenly realized and how euphoric is was for her?) Isaac would have shared the croaking casters' transcendental states since he was part of their link and had his mind "blown," too. I think he's retained much of the the knowledge he gained from that experience, and that's made him "godlike." I don't think he really needs to have the minds of other people inside of him; he's gained so much knowledge that he's going through something like that, anyway. After all, he probably has all of their knowledge now. To him, that would make him godlike.