Storymaker Conference and Me

Just got back from the Storymaker Conference in Provo where I met with an editor from Tor. She said my writing was original, and encouraged me to keep it up. She also said that she thought I could make a living at it.
Now that's what I like to hear.
The only thing that didn't really make sense was when she said I shouldn't worry about getting published right now. When I asked why not? She said it could put me in a niche that would be hard to break out of. I don't really get it. Why would I want to break out of a niche doing something I love to do?
I'm sure she meant well.