Here's a teaser for what he had to say:
There are certainly things I’m surprised I haven’t seen more of, though given the impossibility of keeping up with everything that comes out in the field, I don’t know that I can fairly say that there’s anywhere speculative fiction hasn’t yet gone. That said, and given the success of mixing fantasy and romance, I’m surprised we haven’t seen more in the way of interstitial subgenres.
In particular, given the success of paranormal romance and the rise of steampunk, I’m rather shocked we haven’t seen much in the way of fantasy/western crossovers. Seriously, who wouldn’t be interested in the intersection where Deadwood meets Game of Thrones. The history and mythology of America’s western expansion provides plenty of scope for dark, morally ambiguous stories with tons of drama and very high stakes.