"Rise of Spanish does not predicate decline of English"

Here's a good article on not only why Spanish is becoming so important in the United States, but also why it will never overtake English as the most important language in the country. (A good reason to have top skills in both languages.)

As a translator, it's especially important to have skills in both languages because your skill is only as successful as is your complete understandin of all the nuances in both. If you don't know one very well, chances are you're going to miss something important in some future work that you have to do. - The Japan Times Online