Let's talk about writing in different genres.
Some writers -- like me -- do it for fun, and some do it for fun and money. That, of course, is the difference between me and a professional like Holly Lisle. Holly has a family to feed, clothe and house, and she does it with her writing. At the moment she's trying her hand at a different genre from what she had previously published -- because she has both the talent and the drive to give it a try.
Holly is writing the proposal for a six book romance series -- and she had obviously been working on this for awhile since she already had the critique and notes back from Sheila on the day she got the bad news on her latest fantasy proposal. As it happens, for those who haven't read the material on her site, romance was the first genre she ever wrote a novel in -- at least that's how I remember it. The book didn't sell, but reading Holly's published work, I can see that romance is often an important part of the plot. I suspect she has many romance-sans-fantasy stories in her.
I also know many writers who publish in different genres, and there seems to be a large crossover between the fantasy/sf crowd and the romance group. Sheila Viehl, Rosemary Edghill... It's late and I really can't think of any others right now, but it is not uncommon.
Writing a story is writing a story -- either you have the inspiration and you believe in that story, no matter what the genre, or you aren't going to get very far. I envy the authors who can write romance, for which I have absolutely no talent or interest, which is a huge market. I do try my hand at mystery and YA and children's stories. I would hate to think that being published in one genre meant I could never write in another, or that somehow I would lose all interest in it.
Genre is just a tag. If Holly didn't have an idea for a six book romance series she might have had one for a six book mystery. Or a six book horror, or western... whatever. Stories come from within us, and they don't come with a tag that says 'Oh, I'm not in the genre you've published before. You can't try your hand at me."
I hope Holly does well with the romance books. Reading her blog, I can tell that she's already enjoying the change. I would love to see her blossom into a second career with another income. I know she'd enjoy it.