It may hurt you. I interviewed at a school last year, knowing that I wasn't going to go there because I wanted to try to take a year off, better my application, and get into my first choice school the next year. I had already been rejected by my first choice school about a week before the interview but I decided to still take the interview to just learn about the school and see if I wanted to apply there the next year. When I went into the interview, I told them about how I was planning on taking a year off and I would reapply the next year. I said that I needed a break. I didn't tell them anything about not getting into my first choice school and wanting to try again, I just told them that I wanted to take a year off to work and clear my mind. I reapplied this year to them and they put my application on hold, which it still is. I called and asked them why I didn't get an interview this year but I did last year and they said that it was because of my interview last year and my lack of strong commitment then. From my experiences, it may hurt you to turn down the interview but reapply next year.