Learning a language is great, and it goes beyond being able to do business in a foreign country (or countries.) Learning a new language means also learning a new culture and meeting new people. I strongly encourage people to do it (note to self: pick up Japanese which you've been meaning to do for the past 10+ years.)
However, you don't have to be ... so calculative about it. Learn Italian because you want to read Dante, Spanish to study the nuances of Neruda's poems, French because the ladies dig it (heh), Esperanto because it was a valiant attempt at linguistic utopia, etc.
If you have a vision to work in a specific foreign country, then by all means pick up that language. Otherwise, pick up something that you will enjoy even if it was not business related. Life is not just about positioning yourself for a place in a top MBA school, or success in your career. Learn a language that you're interested it, be it a widely used Latin/Germanic language, or some dying Latin-esque languge that only has snob appeal.
You may intend to work in Northern Africa/South France but your big break might come in a business opportunity in rural India, where Hindi, Urdu or maybe even Sanskrit will be more useful. Don't always plan your life, let serendipity happen to you as well. Most of all, enjoy learning a new language.