I'm getting my Engineering degree next week, and let me tell you something: it is possible to practice a martial art and go to college . I'm the living example and I'm sure there are many more (In fact, one of my teachers is a third dan karate black belt) Just bear in mind that this demands a lot of time an discipline from you, since you have to give your best in school as well as in the Dojo. Since you already have a black belt in your waist, you should have a really good background for practicing other martial arts. Remember that you can always go back to TKD anytime you want, but I recommend the experience of practicing another martial arts (as other people here suggested). You won't "forget" your TKD, nor diminish your TKD training for practicing another MA, I think that what will happen is just the opposite: you'll grow as a martial artist and will have the opportunity to expand your knowledge. I wish you the best of lucks in your college and in your martial arts.