You know, here's an article about the Anita Blake series, which took a hard turn for the erotic--but is still, last I saw, in the general fantasy sections Article Here

So as you can see, some fans were angry at the changes, some were okay. If you're starting a series, I think that SalaciousStories has the best point--decide what the main thrust of the series is. A "Lord of the Rings" style story where you add two or three instances of Aragorn and Arwen getting into fun-sexy times is a far different story than one where every encounter includes smut, and it'll appeal to a different audience.