Karate, BJJ, Muay Thai?

Hi, I've been wondering what I should do with my martial arts 'career' so to speak. I'm 15, and currently doing Shorin-Ryu Karate at a very good dojo. I've been there for 2 years. I have a contract which obligates me to do Karate for at least 2 more years. I'm currently a blue belt, which is the 4th rank out of 10 kyu ranks. Anyway, a good guess is that at the end of these 2 years, I'll be a red, or brown belt (7th and 8th ranks). I could keep going for Black, or switch to a different Martial Art. I think by the end of these 2 years, although I won't be a master, I'll have very solid Karate fighting technique. Afterwards, do you think I should leave and find an MT gym, or broaden my fighting and learn BJJ then maybe do MT later? Also, I'm planning on learning wrestling starting next year at school, although I have no experience yet. What's the best path?