It comes down to what do you think language is for. If you think that it is only for communicating, then the best plan may be "plan Gandelf"Sharkith wrote:No point arguing if you don't get what I am driving it. I prefer diversity and prefer to have it preserved wherever possible. Thats the crux of my disagreement here.

However, if you think language is for culture, then that wiping out the other languages would be a loss.
In either case, a good option is to pick one language and have everyone learn it as a second language if it isn't their first language. English is not the most popular first language, what makes it useful is that it is the most popular 1st + 2nd langage. In fact "pick" is the wrong word. English hasn't been picked as the main language by any one organisation, it is popular because lots of people have made their own choices.
One other thing, having multiple languages divides the world. There potentially would be less wars if everyone could understand each other. OTOH, people would still find ways to create a them and us situation.