English is dominant now, and as you say history shows the dominant lingua francas changes over time - all the time. But I don't think another existing nation's language will take over. Not Spanish, Arabic, Mandarin, etc. Instead, I think an evolved version of English will dominate in 100-200 years time.

We already have many localised Englishes across the world, American, Australian, Indian, various pidgin English, but also in politics, business, social media there are "New Speak" version of English in those contexts.

One of these will evolve to be the lingua franca of the young connected people and dominate. And then be superseded by the next evolved language.

Once we colonize Mars and elsewhere there will be some interesting forks in languages I am sure.