Be honest and specific about your future goals, but consider this, A hiring manager wants to know:

a) If you've set realistic expectations for your career,

b) If you have ambition this interview isn't the first time you're considering the question

c) If the position aligns with your goals and growth. Your best bet is to think realistically about where this position could take you and answer along those lines.

If the position isn't necessarily a one-way ticket to your aspirations? It's OK to say that you're not quite sure what the future holds, but that you see this experience playing an important role in helping you make that decision.