Didn't he do the Wild Cards series of books? That'd make an interesting HBO series.
Syfy already has the rights
to those, and intends to make some kind of movie deal with it.
He's also written a period piece vampire novel set in the American South titled Fevre Dream
, if HBO wants more of that True Blood
lucre... but since his deal is development, I'd assume it would be helping to shape original TV product.