Chinese is already very important, Chinese is starting to compete with English as the lingua franca of business. Spanish is tremendously important in the US and Americas. One language I haven't seen mentioned so far though is Arabic. A fifth of the worlds population is Muslim and while not all of them speak Arabic or even the same dialect of Arabic, Arabic is a tremendously important language for business in the Middle East, North Africa and parts of India and Pakistan. Learning classical arabic would serve you well. On the other hand, if you're doing business in India your choices swing towards Hindi, Urdu or Gujarati. Of course the problem with India is that there are so many different languages spoken.

It all depends on where you're doing business and who you're doing business with.