It is probable that three languages will survive after the middle of this century. Chinese, because of the vast number of people for whom it will be the mother tongue and the two great colonial languages, Spanish and English. These last two languages have spread across the globe since the fourteenth and fifteenth centuries. Their survival is in no small way due to their resilience, adaptability and tolerance of variation.
The Spanish of South America, Mexico and the far east (Philippines) is different from that of metropolitan Spain, especially the spoken language. But in all places there is near perfect understanding by all Spanish speakers.
English is even more flexible. It survives to be understood in spite of different accents and dialects and variations in spelling. Both the spoken and written forms of the language differ from British practice in America and Canada, Australia and New Zealand and across Asia. Even throughout England itself there are a wide variety of accents. If the whole of the United Kingdom is included the variations of the Scots, the Welsh and the Irish are plain to see (in writing) and to hear. Yet all who are literate can comprehend each other. In English more than in any other language it is possible to speak and write it very badly but still be understood.
Chinese is very different in that there are many dialects within the country that are so different that they may truly be considered to be other languages. Speakers in one province frequently cannot understand or converse with those from another. This is changing slowly with the concentration in all schools and government offices being on Mandarin, the Chinese of the Beijing area. The peculiarity remains that there is no phonetic written language. Even stranger is the fact that it is this written language that is universally understood across the nation by literate Chinese regardless of their native regional or provincial spoken tongue.
The sad fact is that of these three great languages it is the peoples of the English speaking countries who exhibit the greatest amount of illiteracy. Many of those for whom English is a first language have very little ability to use it other than in a less than good spoken way. Very often those for whom it is a second language are far better English speakers and writers than those born to it. Proof, if needed, of this deficiency among those in English speaking countries are the constant advertisements on Australian television encouraging those who can neither read nor write to attend classes. Students often end their school days and sometimes leave university without being proficient in English. It is a heavy drag on one’s ability to progress socially and at work if there is a very limited capability in the use of English.
There has been a great concentration over the past decade or so on the teaching of English as a second language. A Google search will reveal many sites offering free instruction in English for non-English speakers. There are not so many offering tuition in basic reading, writing and grammar for those from English speaking countries who lack language skills. One such site is http://www.enufzed.com the very title of which demonstrates just how much English can be tortured and still understood as also do the various pidgin versions of English. It is time that those for whom English is a first language did better.
References: L. J. Sharpe, 2011, http://www.enufzed.com