can i have few points on above mentioned topic.
[CAUTION: I am not a teacher:take the advice and or corrections offered in this post at your own risk.
If you doubt the information, please get a qualified opinion from one of the teachers on these forums.]
In addition to my disclaimer, I feel the need to restate that I am not a teacher am certainly not a "respected" anybody. Still you've posed an interesting question and I would like to offer some personal thoughts as an untrained individual.
Empires have always come to disseminate their language and culture to those areas colonised or conquered. Ironically English's ignominious roots lie in a small tribe being conquered and aopting the language of its conquerors.
We can still see the wide-reaching linguistic impact of French colonisation all over the world in many forms, and England of course is much the same. Incidentally, America has risen to be the leading empire and is able to continue to run on many "English (language) networks laid down in the previous era.
While colonisation per-se has gone out of style, a new kind of "economic colonisation" has taken its place and spreads the language just as much, if not more effectively.
Ultimately however, I imagine sometime in the future English may be displaced as other countries far more populous come to exert global economic influence. Still by that time, English may be a fixture which cannot be removed, but this is in no way certain. Esperanto is an interesting tried-and-failed example of an attempt at a global standard for language, perhaps there will be another based on some other "simple" yet sufficiently functional language.