What is the history of "X is dead. Long live X"?
I feel like I’m missing out on a joke.
Typically it’s used in the phrase, “Le Roi est mort, vive le Roi!” or “The King is dead, long live the King” This means that the (previous) king is dead and we wish the (new) king a long life. It’s also to indicate that there is never a time without a king.
The examples you list typically mean something like, “[language] was bad, now [language] has been improved, or is being used in a totally new way.”