10 years may sound like a long ways away, but the interviewer wants to get an idea if you plan on being in the picture still or not. Avoid stating that you want to take their job or be in their seat, this won't seal the deal. Instead, tell the interviewer that you would like to be in a leadership position or working in a role that would be well suited for someone with 10 years of Medical Transcriptionist experience.
"In 10 years I would like to be finished with nursing school. I've always wanted to help people and currently, this is the way I'd like to start doing that."