The interviewer wants to know whether you have certain expectations about the job that they are unable to fulfil. They are trying to see if there is a match between what you would like, and what they have to offer.
What They Don't Want To Hear
They don't want to hear that you are unrealistic in terms of how quickly you can get promoted, and how far up the organisation you can get. They also don't want to hear that you are so selfish and ambitious that unless you get exactly what you want, you are willing to leave the organisation.
What They Do Want To Hear
They want to hear that you have thought about where you want to go, and that you are realistic in terms of the timeframe of what is possible.
Ask Them How The Promotion Process Works
Ideally what you should do is ask them how their promotion process works within the company, because before you know how it works it's going to be very difficult for you to answer the questions. Also, use this question to check whether there is compatibility between you and your employer in terms of how quickly you want that next promotion. You must make sure they can offer you what you want. If not, there are other jobs.
Good Luck!
