The argument in the above writeup is all very fine and good, and may even point to a real trend. Before you start brushing up on your Esperanto (or whatever), you should take the following point into account:

The number of people for whom English is a second language is probably several times the number of primary speakers. Not only that, many languages have dozens and even hundreds of loanwords from English.

Many widely-spoken "universal" languages (Swahili, Hindi, English) are really combinations of several languages, created when peoples who spoke widely differing languages found themselves living together.

No-one really knows if everyone will eventually wind up speaking the same language, but if they do, it won't be English as she is spoke, it will most likely be some combination of several languages(with a good bit of English thrown in).