In a world of agricultural monocultures, it's not really surprising that languages fade while others become increasingly dominant.
Language is really an artifact of isolation and distance. In an incredibly connected world, the pressure changes from divergence to convergence.
Like other commenters, I have mixed feelings about this. Another used the word "balkanized" (which is a great word) to describe a world divided by incomprehensible language.
Others note that a monoculture isn't the only solution. (Bi|multi)lingualism is another alternative. Multilingualism was the historical response to a world becoming increasingly connected. My great-grandfather grew up in an area where he spoke Russian, French, German and Latvian... by necessity. Depending on which way the political winds were blowing his generation could be conscripted into the Russian or German (maybe Prussian at this point) armies.
That works fine when your sphere is your country and neighbouring countries. But now the sphere is increasingly "the world".
Multilingualism seems to be somewhat cultural and, more importantly, is something that's passed down from one generation to the next. Older children and adults can (and do) acquire new languages with varying success (some are adept, others are not). It seems like if you don't have this from birth you're kinda screwed. If there's no pressure for you to use another language, you're also kinda screwed.
This comes up particularly in the English speaking world where those countries that have English as the predominant first language tend to have no pressure to use another language nor the cultural heritage of multilingualism.
It seems inevitable to me that the world is heading towards a future with a handful of remaining languages. Obvious candidates include English, Arabic, Mandarin, Spanish, Hindi and Russian.