> more certain

Do you doubt that climate change will displace 100s of millions and destroy many large and distinct cultures (e.g. island states) at current emission rates?

That could certainly happen (although the island states I have heard mentioned in this context have populations more in the 10s of thousands), but in terms of culture/language loss this would be a small event compared to the loss in the past/current decades/century, already happening without climate change.