[Is the changing of the setting towards having more prominent magic something GRRM always planned?]

Planned from the beginning.

[Publisher concerns with the graphic content of the series?]

My publishers are perfectly happy with the adult tone of my books. There are plenty of squeaky clean YA fantasies out there for them who don't like that sort of thing,

I do get occasional letters from readers who object to the sexual content in the books... but oddly enough, no one seems to object to the violence. It is a sad commentary on American society that there are people who will be outraged by a description of a penis entering a vagina, but not troubled at all by a description of an axe entering a head.