Mandarin is by far the most widely spoken. Others don't even come close. Cantonese is the other one that people consider common, but... http://www.wolframalpha.com/input/?i=mandarin+%7C+cantonese

There is a non-zero chance of China becoming a larger economic player. Also, China exports a lot of immigrants to other countries. I don't have any data to back this up, but it does not seem like an totally 'out there' idea.