I suppose accents are changing rapidly everywhere. We recently found a recording of my parents talking to me as a baby in the late 1970s. They both sounded like the actors from "The Good Life".
The question is - is it happening more quickly than before. Almost certainly, I'd say, if you listen to examples of London accents across the centuries like these:
> Almost certainly, I'd say, if you listen to examples of London accents across the centuries like these
MAJOR caveat there; to a large extent that's presumably based on people _guessing_ what a London accent was like 600 years ago. There's some evidence, but there certainly aren't recordings, and there'd be ~no information on the small details.
I really noticed this working in a school when I lived in Tennessee. A lot of the faculty had fairly heavy southern accents, but I don't remember ever noticing it with the students. It makes sense though when you realize that a huge chunk of the voices the students learned from were on YouTube, TV, etc., not just people from their own hometown.
The question is - is it happening more quickly than before. Almost certainly, I'd say, if you listen to examples of London accents across the centuries like these:
https://www.youtube.com/watch?v=3lXv3Tt4x20