Specialization Help?

So, I have a question. After completing 50 levels in Halo 4, you can choose a specialization. However, after completing Operator and Wetwork, what can you do? On IGN, an article said that "All the specializations will only be available if you purchase the limited edition or if you played the game between 11.6.12 and 11.20.12. I started playing online on the 13th of November yet I can only see the Operator nad Wetwork specializations. Help?