Of the world’s 6,000 extant languages, roughly 20 have a significant number of speakers (Vietnamese is on the list, for example).
19th century attempts to make a universal language failed with “volapuke” and Esperanto (some history). In the 20th century, however, English accomplished what Esperanto could not.
The world’s disparate languages developed due to isolation. Now that the world has been saturated with communication, the academic linguist does not expect substantial changes going forward. People tend to first learn a more popular language as a second language because it is useful for commerce. But eventually the unpopular language withers and their grandchildren end up being native speakers of what had been the useful second language. Native Americans had at least 300 languages when the European invasion began. Today, however, a Native American such as Elizabeth Warren will grow up speaking English. The same process has occurred in China, where linguistic diversity has shrunk and the comparatively simple second language of Mandarin is now the first language for children. That means that eventually English might eventually be every human’s native language.
Separately, the teacher is a bit of a heretic according to Wikipedia: “McWhorter considers that anti-racism has become as harmful a force in the United States as racism itself. According to him, what is holding blacks back is ‘black attitudes’ rather than white racism. … McWhorter has criticized microaggression and white supremacy theories, and has argued that technology cannot be racist”. Let’s try to imagine how long a white employee of Columbia would last if he/she/ze/they made these kinds of statements!