This question is basically to judge your foresight, knowledge about your domain and in general one’s attitude towards one’s career. By forth one of the most important questions that could be asked - so be very prepared
Hence should not be answered loosely in vague terms and absolutely no dhapugiri. Beginning with retrospection, figure out what you wanna do if you can, tragedy is most of us don’t know for sure what we want to do. Seriously guys do we? (yeah I am reading the fountainhead) So atleast narrow down the options we want to do, whether manager, a consultant, entrepreneur etc. Take your pick and think deeply about it.
Once you have ascertained what you will be doing, try focusing on some aspects further, now by researching your interests and responsibilities arising out of the role that you will be playing. I guess now you hold a clear picture what you will be doing, subject to change of course.
So the answer finally (whew!): Show foresight stating the role you want to fill as of a leader (manager, project lead etc), a worker (developer) an entrepreneur…you know something beyond the mundane and please be confident here. To say you want to be an entrepreneur in a pedestrian way will be irritating. Say what you think will be the future in your domain..like you see advanced mobile apps in JAVA or rural networking. Convince them you know whats in store for YOU and how you can/will CONTRIBUTE to this vision. Give them relevant examples ,hello research . If possible a time frame. And finally tell them how you tend to achieve all this, by learning further or gaining experience.
This answer I feel is as endless as one’s avenues and I feel is one that should be answered honestly by everyone, literally on a piece of paper. Do this atleast twice. I Guarantee a positive result in many ways.