My best girl friend just got back from the Disney College Program in January. During the intervening months she has spent a lot of time on the cell phone (nights and weekends of course), using the internet to keep in touch with people, and visiting those who are within a car ride of where we live. So it IS possible to keep in touch--you just have to be willing to work at it.
She has also applied for the advanced internship program and will probably be doing another "tour of duty" so to speak, like most of her friends from there have. You won't lose all your friends from Disney--trust me, it's not possible