New words are being introduced constantly. The Dutch and Belgian word of the year 2013 is "selfie". Even the Oxford dictionary proclaimed this to be the word of the year. The question is, to which language does this word belong? You might say English, but the chances are that we will forget that after many years. Just as we did for many other words.
Because of internet and other ways people from different continents intermingle, this process will accelerate. One might already notice that English written and spoken on internet has somewhat specific vocabulary, often influenced by or made up by technical people among us. Many of these words are only used in reference to internet. E.g. googling.
With increasing Chinese influence, it is becoming very attractive to learn Mandarin. The obvious effect will be introduction of Mandarin words outside China.
It is often discussed which country speaks and writes English in the most correct way. This became very evident when I came to Hong Kong. I had and still have hard time communicating with Hongkongers, even when they speak English. This excludes peoples who lived or studied in England or some other English speaking country. One might find Hong Kong English pretty lousy, until I realised they do communicate to each other and other Asians pretty well in English. So, there must be something wrong with me?! Well, I'm not afraid to admit my shortcomings, specially with all grammar mistakes in this post. Still, I would not say my English is bad.
Eventually, there will be no such thing as bad spoken English. This should, and will be replaced by how well two people understand each other. I have already witnessed this on international IT conferences or networking events. People speak English in so many different ways, that I eventually started to forget what the correct English suppose to sound. In my case, this is for some reason English spoken in London.
For anyone familiar with Star Trek, it looks like everyone, even aliens from other planets come from USA, actually California. They all have pretty much the same English accent. That might seem completely wrong assumption, but only unlikely part here is that they will speak English with this specific accent.
In the coming 100 years, this so called English, will change much faster simply because people influence each other more than ever, and maybe because Asian countries are influencing the rest of the world more and more. In 100 years, that will be a new kind of language, full of new words, many technological. The grammar will also be more simplified, as many countries have great difficulty understanding difference between "has been" and "had been" as one of the examples.
This new language will come at price that we must pay and not regret. Many, if not all of the existing languages will become secondary and slowly start disappearing from our daily use. Still, having a one language that unites us, is maybe the best recipe for solving our conflicting differences.