You are right that a lot of the culture might fade away with the change of language. My grandmother used to speak a dialect called "Low German" in her childhood. When I was born, it had more or less completely faded away. She also feels sadness that no one was talking it anymore. When she meets her brothers and sisters, they always start to talk in this dialect when they speak to each other.

I haven't experienced such a change firsthand, so I might be a bit too harsh with my more positive view on it.