It is true that some languages are being spoken widely in various nations and the use of a few languages is declining. While there are some negative developments of this trend, I believe the positive developments are much more.
There are a number of positive effects of the increasing use of some languages. One possible positive effect is that it easing communication among people. By learning languages widely, people can easily communicate with others nation people and they will not face difficulty when they travel to another country. Furthermore, if people speak the same language, then they also find it easy to do business with each other. Because global trade is based on good communication. Another positive effect is that it is helpful in getting job. For example, multinational companies have opened in different parts of the world. So, the rich nations who own this multinational companies provide jobs to millions of people worldwide. Naturally a person who knows their language is better placed in these companies.
Despite the positive development mentioned above, the decline in use of some languages has some negative effects too. To begin with, it is a well-known fact that language and culture are interrelated. If any countries language dies out then the culture of those countries also dies out. Moreover, we all enjoy life on this planet because of its diversity. If diversity decreases, then boredom sets in and the earth becomes a dull and boring place to live.
In conclusion, although there are some negative outcomes of increasing use of some languages, I would argue that the decline of other languages is more positive than negative.