It is quite interesting to talk about a single world language, English has that potential and will be in that position within 50 or 100 years! But our mother tongues and cultures have to be preserved at any cost!

No language have such a property. It is said that each and every language which grows in size will collapse and perhaps divide into other languages. It is suspected that this happened to many extinct languages. This is some information theory related bound. I am not an expert. And I have no citations right now. English is in immense pressure to be honest because of the surge of words and usages from many languages. There is a possibility that the language collapses. But I don't know how and why even!