Earlier quoted context omitted.
“There will exist 500 year old actively serviced BBS phone lines” —someone in 1985, probably
The thing is there can't be more than one internet, ever. The moment someone invents a new internet, someone will create a gateway to the old internet, and the internet will live on.
The old internet could disappear as long as the economical incentives are enough to transition to a new centralized form of internet.
We are far from it, thanks, but don’t neglect that Facebook made a ton of websites become useless (to their owner at least) and disappear. Also, networks operators have made low cost plans limited to some of the internet. This is far from enough to kill the internet but a more restricted network is totally amongst the possibilities. And I’m not even talking about state control like in China.