If history and human and society go on as they have done, then yes, there are centripetal and centrifugal pressures on language: communities want to be understandable within each other, but communities also want to sound distinct from each other. The community you identify with in your daily (or weekly) linguistic interactions determines the boundaries of your language.
But in a future where transhumanism is a possibility—as is the extinction of humanity—I’m not sure we can assume that things will go on as they have.
Things have already changed significantly, even without robot overlords or global catastrophe. The centripetal forces are getting stronger, and the centrifugal forces are getting weaker.
The community of interaction, which used to be at most the villages feeding into the local market town, has become the nation under nationalism and mass media, which has led to mass die-off of dialects, and attenuation in social status of regional languages. This is an attenuation which is often the precursor to language death: a language that only gets used in the hearth, and has retreated from the public domain, does not compete well with languages with full Ausbau (Abstand and ausbau languages).
And that trend is only increasing. Many communities and contexts of interaction are now global. If a university course in IT in Greece is conducted in English, that means that there’s already one professional domain that Greek has given up on. And that really is how it starts.
Yes, people in Athens will still want to sound different from people in New York. But you don’t need a separate language like that, or even a separate dialect. A separate accent would do. That in itself won’t guarantee the survival of Greek.
Collapse of national languages in the face of English would require comprehensive undermining of the nation-state, as other respondents have argued. But that’s really not unimaginable.