Thankfully, fears that English will become the world’s only language are premature. Few are so pessimistic as to suppose that there will not continue to be a multiplicity of nations and cultures on our planet and, along with them, various languages besides English. It is difficult, after all, to interrupt something as intimate and spontaneous as what language people speak to their children. Who truly imagines a Japan with no Japanese or a Greece with no Greek? The spread of English just means that earthlings will tend to use a local language in their own orbit and English for communication beyond.
But the days when English shared the planet with thousands of other languages are numbered. A traveler to the future, a century from now, is likely to notice two things about the language landscape of Earth. One, there will be vastly fewer languages. Two, languages will often be less complicated than they are today—especially in how they are spoken as opposed to how they are written.
Some may protest that it is not English but Mandarin Chinese that will eventually become the world’s language, because of the size of the Chinese population and the increasing economic might of their nation. But that’s unlikely. For one, English happens to have gotten there first. It is now so deeply entrenched in print, education and media that switching to anything else would entail an enormous effort. We retain the QWERTY keyboard and AC current for similar reasons.