English has reached enough of a critical mass by now that even if north America and the UK would fall off the surface of the earth tomorrow, it would take a few generations for another language to take it's place as a medium for international exchange. Newton wrote in Latin more than 1000 years after the empire left Britain.
Bad second language English (like e.g. mine, I feel quite at home in writing, but you should see me navigating the linguistic perils of a US supermarket checkout, not funny) is close to useless when talking to native speakers, but it can be invaluable as a common ground with other non-native speakers.
Bad second language English (like e.g. mine, I feel quite at home in writing, but you should see me navigating the linguistic perils of a US supermarket checkout, not funny) is close to useless when talking to native speakers, but it can be invaluable as a common ground with other non-native speakers.