Since the rise of the web, and tv and movies before it, regional language divergence is decreasing instead of increasing as it did in the past. Future English will be more globally unified but with more online text chatting influences.
Sure, if the educational system today collapses and we revert to pre-industrial state like around 500 AD, English will spontaneously develop into a family of mutually unintelligible languages.
I sincerely hope that this won't happen, though, because 95 per cent of humanity would die. We cannot feed 8 billion people with pre-modern technology.
edit: If we're not killed by corruption, the assumption is that people will be enjoying films made in the 1920's and 30's in the 2220's and the 2230's. That's completely unprecedented, and has to pin a language to a certain extent.
Imagine if during the Great Vowel Shift, everybody could listen (and did listen, for entertainment) to people speaking at length from before. It would have ended up a fashion where maybe a couple of features stuck.
In 2230, there will be 300 years of film to watch. The past will overwhelm the present.