Crisis: The time to learn a new language

Is English enough? The answer is probably not. Even if you are or not an English native speaker I would recommend you to walk across that boundary and start learning any other language.
English is the international language for business or travelling around the world. I am sure you will not have any problem at communication if you are able to manage English with a bit of fluency. But times are changing and cultures and languages which formerly were not so important are becoming increasingly influential in the modern world.
According to the number of speakers, Mandarin, Spanish, English, Hindu and Arabic are the top five languages today. Should we learn those tongues? This is hard to answer.
China is a new economy, with an incredible influential power. More and more firms are moving to China some key components of their business and focusing at the Asian market.
Learning Mandarin will bring you lot of professional opportunities if you do not care about moving into a foreign country.
What about Europe? After English and German, the focus is located on Russian. Upper class in Russia has a powerful economy and is really attracted by the Mediterranean coast. If you live around the Mediterranean Sea (Spain, France, Italy, Greece...), learning Russian is not a bad choice at all. Services industry is focusing on Russian tourists and there already are some accommodation agencies, boat makers or luxury restaurants which are looking for Russian speakers, in order offer a personalized service, taking care of the customer.
What would be the recommendation? If you are able to manage in English but you fluency is not enough to use it on a professional field, improve it. You can start download movies and series in English using subtitles, listen podcast or sign up for a conversation group through Skype.
If English is not a problem at all, think about your next step. If you are attracted by remote and exotic cultures, the Russian or Mandarin languages can be a motivation, but when your action field is Europe: German or French are your best choice.