Hi,
When I was getting ready to submit my proposal the potential supervisors did ask to meet and discuss the study, this was primarily to see how passionate and motivated you are for the study (almost like a pre-screening). I would recommend that you prepare something to take with you to your meeting, along the lines of why you want to research this topic, a possible methodology, your previous experiences with the topic and why you're choosing to study at that particular university. The potential supervisor will also want to see if your personalities match, if he/she thinks you're not motivated enough for they study they won't help you as much with the proposal. So be keen and prepared but don't get nervous and be yourself.
Hope this helps.
All the best.